2492 + Interview Questions in CURRENT-ELECTRICITY IN GENERAL AWARENESS Page 40 InterviewSolution

1951.	For what value of unknown resistance `X`, the potential difference between `B` and `D` will be zero in the circuit shown in the figure ? A. `4 Omega`B. `6 Omega`C. `2 Omega`D. `5 Omega`
Answer» Correct Answer - B (b) For balanced Wheatstone bridge` (P)/(Q) = (R )/(S)` `implies (12)/((1//2)) = (x + 6)/((1//2)) implies x = 6 Omega`

Discussion

1952.	Two electric bulbs of `40` watt each are connected in series. The power consumed by the combination will beA. 20 wattB. 60 wattC. 80 wattD. 100 watt
Answer» Correct Answer - a

Discussion

1953.	Two bulbs which consume powers `P_(1) " and P_(2)` are connected in series. The power consumed by the combination isA. `P_(1)+P_(2)`B. `sqrt(P_(1)P_(2)`C. `(P_(1)P_(2))/(P_(1)+P_(2))`D. `(2P_(1)P_(2))/(P_(1)+P_(2))`
Answer» Correct Answer - A For a series circuit, `R_(s)=R_(1)+R_(2)` `rArri^(2)R_(s)=i^(2)R_(1)+i^(2)R_(2)rArrP_(s)=P_(1)+P_(2)`

Discussion

1954.	Specific resistance of copper, silver and constantan are `(1.78 xx 10^(-6) Omega cm, 10^(-6) Omega cm and 48 xx 10^(-6) Omega cm`) respectively. Which is the best conductor and why?
Answer» The best conductor is silver because electrical conductivity is inversely proportional to the resistivity and resistivity of silver is least.

Discussion

1955.	What are the materials generally used for making standard resistance? Give their compositions .
Answer» (i) Constantan `[Cu(60%) + Ni(40%)]` (ii) Manganin `[Cu (84%) +Mn(12%)+Ni(4%)]`

Discussion

1956.	What are the materials generally used for making standard resistance? Give their compositions .A. nichromeB. copperC. silverD. maganin
Answer» Correct Answer - D

Discussion

1957.	A steady current flow in a metallic conductor of non-uniform cross-section. The quantity/quantities remaining constant along the whole length of the conductor is /are.A. current, electric field and drift speedB. drift speed onlyC. current and drift speedD. current only
Answer» Correct Answer - D In a metallic conductor of non-uniform cross-section, only the current remains constant along the entire length of the conductor.

Discussion

1958.	If internal resistance of a cell is proportional to current drawn from the cell. Then the best representation of terminal potential difference of a cell with current drawn from cell will beA. B. C. D.
Answer» Correct Answer - D

Discussion

1959.	The flow of the electric current through a metallic conductor isA. only due to electronsB. only due to `+ve` chargesC. due to both nuclei and electrons.D. can not be presicted
Answer» Correct Answer - A

Discussion

1960.	If internal resistance of a cell is proportional to current drawn from the cell. Then the best representation of terminal potential difference of a cell with current drawn from cell will beA. B. C. D.
Answer» Correct Answer - D

Discussion

1961.	The quantity in electricity analogous to friction in linear mechanical motion isA. resistanceB. potentialC. chargeD. inductance
Answer» Correct Answer - A

Discussion

1962.	The quantity in electricity analogous to temperature isA. resistanceB. potentialC. chargeD. inductance
Answer» Correct Answer - B

Discussion

1963.	In an electric circuit containing a battery,the charge (assumed positive )inside the battery.A. always goes from the positive terminal to the negative terminalB. may go from th positive terminal to the negative terminalC. always goes from the negative terminal to the positive terminalD. does not move.
Answer» Correct Answer - B

Discussion

1964.	Temperature is analogous to what in electricity?A. potentialB. resistanceC. currentD. charge
Answer» Correct Answer - A

Discussion

1965.	In an electric circuit containing a battery,the charge (assumed positive )inside the battery.A. always goes form the positive terminal to the negative terminalB. may move from the positive terminal to the negative terminalC. always gows from the negative terminal to the positive terminalD. does not move.
Answer» Correct Answer - B

Discussion

1966.	Electric field (E) and current density `(J)` have relationA. `EpropJ^(-1)`B. `EpropJ`C. `Eprop(1)/(J^(2))`D. `E^(2)prop(1)/(J)`
Answer» Correct Answer - B

Discussion

1967.	`I-V` characterstic of a copper wire of length `L` and area fo cross-section `A` is shown in Fig. The slope of the curve becomes A. More if the experiment is performed at higher temperatureB. More if a wire of stell of same dimension is usedC. More if the length of the wire is increasedD. Less if the length of the wire is increased
Answer» Correct Answer - D

Discussion

1968.	Assertion: A current flows in a conductor only when there is an electric field within the conductor: Reason: The drift velocity of electron in presence of electric field decreases.A. Both (A) and (R) are true and (R) is the correct explanantion of A.B. Both (A) and (R) are true but (R) is not the correct explanation of A.C. (A) is true but (R) is falseD. (A) is false but (R) is true.
Answer» Correct Answer - C

Discussion

1969.	When a current flows in a conductor, the order of magnitude of drift velocity of electrons through it is :A. `10^(10)cm//s`B. `10^(4)cm//s`C. `10^(-2) cm//s`D. `10^(-7)cm//s`
Answer» Correct Answer - C

Discussion

1970.	From the graph between current I and voltage V shown below, identify the portion corresponding to negative resistanc A. ABB. BCC. CDD. DE
Answer» Correct Answer - C

Discussion

1971.	Assertion : Current flows in a conductor only when there is an external electric field within the conductor. Reason: The drift velocity of the electrons is directly proportional to the electric field.A. If both assertion and reason are true and reason is the correct explantion of assertion.B. If both assertion and reason are true and reason is not the correct explantion of assertion.C.D. If assertion is true but reason is false.
Answer» Correct Answer - A In the absence of electric field, the electrons move randomly in all directions. Hence there is no net motion of electrons and no current flow in the conductor. But in the presence of electric field, electrons move in a particular direction. Each electron experiences a force in the direction opposite to that of the electric field and moves from the negative end to the positive end of the conductor. Thus there is a current flow. The drift velocity,

Discussion

1972.	From the given between current I and voltage V shown in figure , indentify the portion corresponding to negative resistance A. DEB. CDC. BCD. AB
Answer» Correct Answer - B

Discussion

1973.	The current in the following circuit is A. `1A`B. `(2)/(3)A`C. `(2)/(9)A`D. `(1)/(8)A`
Answer» Correct Answer - A

Discussion

1974.	An total resistance `R` is connected to a cell of internal resistance `r` the maximum current flows in the external resistance, whenA. `R = r`B. `R lt r`C. `R gt r`D. `R = r//2`
Answer» Correct Answer - A

Discussion

1975.	Three copper wires of length and cross-sectional areas are (L,A)`(2L,(A)/(2)),(L//2,2A)`, resistance isA. minimum in wire of cross-sectional area `(A)/(2)`B. minimum in wire of cross-sectional area AC. minimum in wire of cross-sectional area 2AD. same in all three cases
Answer» Correct Answer - C `l_(1)=L,A_(1)=A` `l_(2)=2L, A_(2)=(A)/(2)` `(R_(1))/(R_(2))=(l_(1))/(l_(2))xx(A_(2))/(A_(1)) implies R_(3) lt R_(1) lt R_(2)`

Discussion

1976.	An total resistance `R` is connected to a cell of internal resistance `r` the maximum current flows in the external resistance, whenA. `R = r`B. `R lt r`C. `R gt r`D. none of the above
Answer» Correct Answer - A

Discussion

1977.	Two wire of copper have length `L` and `2L` and cross section `2A` and A respectively .The ratio of their specific resistance would be would beA. `1:2`B. `8:1`C. `1:8`D. `1:1`
Answer» Correct Answer - D

Discussion

1978.	The Total resistance when connected in series in `9 Omega` and when connected in parallel is `2 Omega` The value of two resistance areA. `4 Omega and 5 Omega`B. `2 Omega and 7 Omega`C. `3 Omega and 6 Omega`D. `1 Omega and 8 Omega`
Answer» Correct Answer - C

Discussion

1979.	Define resistivity of the material. State its SI unit and discuss its variation with temperature in case of (i) metals (ii) semiconductors and (iii) insulators.A. increasedB. decreasesC. becomes zeroD. remains constant
Answer» Correct Answer - A

Discussion

1980.	In the circuit shown in figure A. current in wire AF is 1AB. current in wire CD is 1AC. current in wire BE is 2AD. None of these
Answer» Correct Answer - D

Discussion

1981.	Sixty per cent of given sample of oxygen gas when raised to a high temperature dissociates into atoms Ratio of its initial heat capacity (at constant volume) to the final heat capacity (at constant volume) will beA. `(8)/(7)`B. `(25)/(26)`C. `(10)/(7)`D. `(25)/(27)`
Answer» Correct Answer - C

Discussion

1982.	The root mean spuare (rms) speed of hydrogen molecules at a certain temperature is 300m/s. If the temperature is doubled and hydrogen gas dissociates into atomic hydrogen the rms speed will becomeA. `424.26m//s`B. `300m//s`C. `600m//s`D. `150m//s`
Answer» Correct Answer - C

Discussion

1983.	A copper sphere is suspended in an evacuated chamber maintained at `300 K`. The sphere is mantained at a constant temperature of `500 K` by heating it electrically. A total of `300 W` of electric power is needed to do it. When half of the surface of the copper sphere is completely blackened, `600W` is needed to maintain the same temperature of the the sphere. Calculate the emissivity of copper.A. `(1)/(4)`B. `(1)/(3)`C. `(1)/(2)`D. `(1)/(5)`
Answer» Correct Answer - B

Discussion

1984.	Which of the following I-V graph represents ohmic conductors?A. B. C. D.
Answer» Correct Answer - A For ohmic resistance, the graph between V and I is straight line and it passes through origin.

Discussion

1985.	The drift velocity does not depend uponA. Cross-section of the wireB. Length of the wireC. Number of free electronsD. Magnitude of the current
Answer» Correct Answer - B

Discussion

1986.	There is a current of 40 ampere in a wire of `10^(-6)m^(2)` are of cross-section. If the number of free electron per `m^(3)` is `10^(29)` then the drift velocity will beA. `1.25 xx 10^(3) m//s`B. `2.50 xx 10^(-3)m//s`C. `25.0 xx 10^(-3)m//s`D. `250 xx 10^(-3)m//s`
Answer» Correct Answer - B

Discussion

1987.	At room temperature copper has free electron density of `8.4xx10^(28) per m^(3)` . The copper conductor has a cross-section of `10^(-6)m^(2)` and carries a current of 5.4 A. What is the electron drift velocity in copper?A. `400 m//s`B. `0.4 m//s`C. `0.4 mm//s`D. `72 m//s`
Answer» Correct Answer - C

Discussion

1988.	You are given a wire of length 100 cm and linear resistance of 1 ohm/cm. if it is cut into two parts, so that when they are in parallel, the effective resistance is 24 ohm. The lengths of the two parts areA. 30 cm & 70 cmB. 60 cm & 40 cmC. 70 cm & 30 cmD. 20 cm & 80 cm
Answer» Correct Answer - B combination of resistors

Discussion

1989.	The resistance will be least in a wire with length, cross-section area respectively,A. L/2, 2AB. 2L, AC. L, AD. L, 2A
Answer» Correct Answer - A Resistance `R = rho l ..A` or `R prop l //A`. `therefore " " R_(a)prop(L)/(4A), R_(b)prop (2L)/(A), R_(c )prop(L)/(A)`. Thus, resistance is least in a wire of length L/2 and area of cross-section is 2A.

Discussion

1990.	When a current flows through a conductor its temperatureA. May increase or decreaseB. Remains sameC. DecreasesD. Increases
Answer» Correct Answer - D

Discussion

1991.	Two wires of same material have length L and 2 L and cross– sectional areas 4 A and A respectively. The ratio of their specific resistance would beA. `1:2`B. `8:1`C. `1:8`D. `1:1`
Answer» Correct Answer - D For same material specific resistance will be same.

Discussion

1992.	Equivalent resistance between points A and B is `0.5 xR.` Find value of x. A. 3RB. 4RC. `(5R)/(2)`D. `(7R)/(2)`
Answer» Correct Answer - C

Discussion

1993.	Two wires of same material have length L and 2 L and cross– sectional areas 4 A and A respectively. The ratio of their specific resistance would beA. `1 :2`B. `8 :1`C. `1 :8`D. `1 :1`
Answer» Correct Answer - D

Discussion

1994.	All resistance shown in the circuit are `2Omega` each. The current in the resistance between `D` and `E` is A. 5AB. `2.5`AC. 1AD. `7.5`A
Answer» Correct Answer - B

Discussion

1995.	A capacitor is charged up to a potneital `V_(0)` It is then connected to a resistance R and a battery of emf E. Two possible graphs of potential difference across capacitor with time are shown. What is the most reasonable explanation of these graphs? A. The first graph shows what happens when the capacitor has potential difference less than E initially and the second shows what happens when it has potential difference greater than E initially:B. The first graph shows what happens when the capacitors has potential difference greater than E initially and the second shows what happens when it has a less than E potential initiallyC. The first graph is the correct qualitative shape for any initial potential across capacitor, but the second is not possibleD. The second graph is the correct qualitative shape for any initial potential difference across capacitor, but the first is not possible.
Answer» Correct Answer - B

Discussion

1996.	In the circuit shown, keys `K_1` and `K_2` both are closed the ammeter reads `I_0`. But when `K_1`is open and `K_2` is closed, the ammeter reads `I_0//2`. Assuming that ammeter resistance is much less than `R_2`, the values of `r` and `R_1` is Omega are A. 25,50B. 25100C. 0,100D. 0,50
Answer» Correct Answer - D When `K_1` and `K_2` both are closed `R_1` is short circuited, `R_("net")=(50+r)Omega` When `K_1` is open and `K_2` is closed, current remains half. Therefore, net resistance of the circuit becomes two times. or `(50+r)+R_1=2(50+r)` of the given options the above equation is satisfied if `r=0` and `R_1 =50 Omega`

Discussion

1997.	A copper wire has a square cross-section, 2.0 mm on a side. It carries a current of 8 A and the density of free electrons is `8 xx 10^(28)m^(-3)`. The drift speed of electrons is equal toA. `0.156 xx 10^(-3) ms`B. `0.156 xx 10^(-2)ms`C. `3.12 xx 10^(-3)ms`D. `3.12 xx 10^(-2)ms`
Answer» Correct Answer - A

Discussion

1998.	A battery of e.m.f. `10 V` is connected to resistance as shown in figure. The potential difference `V_(A) - V_(B)` between the point `A` and `B` is A. `-2V`B. 2VC. 5VD. `(20)/(11)V`
Answer» Correct Answer - B

Discussion

1999.	In the circuit shown, keys `K_1` and `K_2` both are closed the ammeter reads `I_0`. But when `K_1`is open and `K_2` is closed, the ammeter reads `I_0//2`. Assuming that ammeter resistance is much less than `R_2`, the values of `r` and `R_1` is Omega are A. 100,50B. 50100C. 0,100D. 0,50
Answer» Correct Answer - D

Discussion

2000.	The resistance of an incandescent lamp isA. Greater when switched offB. Smaller when switched onC. Greater when switched onD. The same whether it is switched off or switched on
Answer» Correct Answer - C

Discussion

Explore topic-wise InterviewSolutions in .

For what value of unknown resistance `X`, the potential difference between `B` and `D` will be zero in the circuit shown in the figure ? A. `4 Omega`B. `6 Omega`C. `2 Omega`D. `5 Omega`

Two electric bulbs of `40` watt each are connected in series. The power consumed by the combination will beA. 20 wattB. 60 wattC. 80 wattD. 100 watt

Two bulbs which consume powers `P_(1) " and P_(2)` are connected in series. The power consumed by the combination isA. `P_(1)+P_(2)`B. `sqrt(P_(1)P_(2)`C. `(P_(1)P_(2))/(P_(1)+P_(2))`D. `(2P_(1)P_(2))/(P_(1)+P_(2))`

Specific resistance of copper, silver and constantan are `(1.78 xx 10^(-6) Omega cm, 10^(-6) Omega cm and 48 xx 10^(-6) Omega cm`) respectively. Which is the best conductor and why?

What are the materials generally used for making standard resistance? Give their compositions .

What are the materials generally used for making standard resistance? Give their compositions .A. nichromeB. copperC. silverD. maganin

A steady current flow in a metallic conductor of non-uniform cross-section. The quantity/quantities remaining constant along the whole length of the conductor is /are.A. current, electric field and drift speedB. drift speed onlyC. current and drift speedD. current only

If internal resistance of a cell is proportional to current drawn from the cell. Then the best representation of terminal potential difference of a cell with current drawn from cell will beA. B. C. D.

The flow of the electric current through a metallic conductor isA. only due to electronsB. only due to `+ve` chargesC. due to both nuclei and electrons.D. can not be presicted

If internal resistance of a cell is proportional to current drawn from the cell. Then the best representation of terminal potential difference of a cell with current drawn from cell will beA. B. C. D.

The quantity in electricity analogous to friction in linear mechanical motion isA. resistanceB. potentialC. chargeD. inductance

The quantity in electricity analogous to temperature isA. resistanceB. potentialC. chargeD. inductance

Temperature is analogous to what in electricity?A. potentialB. resistanceC. currentD. charge

Electric field (E) and current density `(J)` have relationA. `EpropJ^(-1)`B. `EpropJ`C. `Eprop(1)/(J^(2))`D. `E^(2)prop(1)/(J)`

When a current flows in a conductor, the order of magnitude of drift velocity of electrons through it is :A. `10^(10)cm//s`B. `10^(4)cm//s`C. `10^(-2) cm//s`D. `10^(-7)cm//s`

From the graph between current I and voltage V shown below, identify the portion corresponding to negative resistanc A. ABB. BCC. CDD. DE

From the given between current I and voltage V shown in figure , indentify the portion corresponding to negative resistance A. DEB. CDC. BCD. AB

The current in the following circuit is A. `1A`B. `(2)/(3)A`C. `(2)/(9)A`D. `(1)/(8)A`

An total resistance `R` is connected to a cell of internal resistance `r` the maximum current flows in the external resistance, whenA. `R = r`B. `R lt r`C. `R gt r`D. `R = r//2`

Three copper wires of length and cross-sectional areas are (L,A)`(2L,(A)/(2)),(L//2,2A)`, resistance isA. minimum in wire of cross-sectional area `(A)/(2)`B. minimum in wire of cross-sectional area AC. minimum in wire of cross-sectional area 2AD. same in all three cases

An total resistance `R` is connected to a cell of internal resistance `r` the maximum current flows in the external resistance, whenA. `R = r`B. `R lt r`C. `R gt r`D. none of the above

Two wire of copper have length `L` and `2L` and cross section `2A` and A respectively .The ratio of their specific resistance would be would beA. `1:2`B. `8:1`C. `1:8`D. `1:1`

The Total resistance when connected in series in `9 Omega` and when connected in parallel is `2 Omega` The value of two resistance areA. `4 Omega and 5 Omega`B. `2 Omega and 7 Omega`C. `3 Omega and 6 Omega`D. `1 Omega and 8 Omega`

Define resistivity of the material. State its SI unit and discuss its variation with temperature in case of (i) metals (ii) semiconductors and (iii) insulators.A. increasedB. decreasesC. becomes zeroD. remains constant

In the circuit shown in figure A. current in wire AF is 1AB. current in wire CD is 1AC. current in wire BE is 2AD. None of these

Sixty per cent of given sample of oxygen gas when raised to a high temperature dissociates into atoms Ratio of its initial heat capacity (at constant volume) to the final heat capacity (at constant volume) will beA. `(8)/(7)`B. `(25)/(26)`C. `(10)/(7)`D. `(25)/(27)`

The root mean spuare (rms) speed of hydrogen molecules at a certain temperature is 300m/s. If the temperature is doubled and hydrogen gas dissociates into atomic hydrogen the rms speed will becomeA. `424.26m//s`B. `300m//s`C. `600m//s`D. `150m//s`

Which of the following I-V graph represents ohmic conductors?A. B. C. D.

The drift velocity does not depend uponA. Cross-section of the wireB. Length of the wireC. Number of free electronsD. Magnitude of the current

There is a current of 40 ampere in a wire of `10^(-6)m^(2)` are of cross-section. If the number of free electron per `m^(3)` is `10^(29)` then the drift velocity will beA. `1.25 xx 10^(3) m//s`B. `2.50 xx 10^(-3)m//s`C. `25.0 xx 10^(-3)m//s`D. `250 xx 10^(-3)m//s`

At room temperature copper has free electron density of `8.4xx10^(28) per m^(3)` . The copper conductor has a cross-section of `10^(-6)m^(2)` and carries a current of 5.4 A. What is the electron drift velocity in copper?A. `400 m//s`B. `0.4 m//s`C. `0.4 mm//s`D. `72 m//s`

You are given a wire of length 100 cm and linear resistance of 1 ohm/cm. if it is cut into two parts, so that when they are in parallel, the effective resistance is 24 ohm. The lengths of the two parts areA. 30 cm & 70 cmB. 60 cm & 40 cmC. 70 cm & 30 cmD. 20 cm & 80 cm

The resistance will be least in a wire with length, cross-section area respectively,A. L/2, 2AB. 2L, AC. L, AD. L, 2A

When a current flows through a conductor its temperatureA. May increase or decreaseB. Remains sameC. DecreasesD. Increases

Two wires of same material have length L and 2 L and cross– sectional areas 4 A and A respectively. The ratio of their specific resistance would beA. `1:2`B. `8:1`C. `1:8`D. `1:1`

Equivalent resistance between points A and B is `0.5 xR.` Find value of x. A. 3RB. 4RC. `(5R)/(2)`D. `(7R)/(2)`

Two wires of same material have length L and 2 L and cross– sectional areas 4 A and A respectively. The ratio of their specific resistance would beA. `1 :2`B. `8 :1`C. `1 :8`D. `1 :1`

All resistance shown in the circuit are `2Omega` each. The current in the resistance between `D` and `E` is A. 5AB. `2.5`AC. 1AD. `7.5`A

In the circuit shown, keys `K_1` and `K_2` both are closed the ammeter reads `I_0`. But when `K_1`is open and `K_2` is closed, the ammeter reads `I_0//2`. Assuming that ammeter resistance is much less than `R_2`, the values of `r` and `R_1` is Omega are A. 25,50B. 25100C. 0,100D. 0,50

A copper wire has a square cross-section, 2.0 mm on a side. It carries a current of 8 A and the density of free electrons is `8 xx 10^(28)m^(-3)`. The drift speed of electrons is equal toA. `0.156 xx 10^(-3) ms`B. `0.156 xx 10^(-2)ms`C. `3.12 xx 10^(-3)ms`D. `3.12 xx 10^(-2)ms`

A battery of e.m.f. `10 V` is connected to resistance as shown in figure. The potential difference `V_(A) - V_(B)` between the point `A` and `B` is A. `-2V`B. 2VC. 5VD. `(20)/(11)V`

In the circuit shown, keys `K_1` and `K_2` both are closed the ammeter reads `I_0`. But when `K_1`is open and `K_2` is closed, the ammeter reads `I_0//2`. Assuming that ammeter resistance is much less than `R_2`, the values of `r` and `R_1` is Omega are A. 100,50B. 50100C. 0,100D. 0,50

The resistance of an incandescent lamp isA. Greater when switched offB. Smaller when switched onC. Greater when switched onD. The same whether it is switched off or switched on