Practice the Class 7 Science MCQ Questions of Electric Current and Its Effects with Answers. MCQ Questions for Class 7 Science with Answers were arranged dependent on the most recent pattern of the exam. We have Provided Electric Current and Its Effects Class 7 Science MCQ Questions with Answers to help understudies comprehend the idea well indeed. 

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Practice MCQ Questions for Class 7 Science

1. In making a battery

(a) positive terminal of one cell is connected to the negative terminal of the next cell
(b) positive terminal of one cell is connected to the positive terminal of the next cell
(c) negative terminal of one cell is connected to the negative terminal of the next cell
(d) none of the above

2. Where can the key or switch be placed in the circuit?

(a) Left side of the battery
(b) Right side of the battery
(c) Can be placed anywhere in the circuit
(d) Near the positive terminal of the bulb

3.The coil of wire contained in an electric heater is known as

(a) component
(b) element
(c) circuit
(d) spring

4. Which mark is necessary on electric appliances?

(a) AGMARK
(b) ISI
(c) FICCI
(d) KSK

5. When a switch is in OFF position.

(i) circuit starting from the positive terminal of the cell stops at the switch.
(ii) circuit is open.
(iii) no current flows through it.
(iv) current flows after some time.

Choose the combination of correct answer from the following:

(a) all are correct
(b) (ii) and (iii) are correct
(c) only (iv) is correct
(d) only (i) and (ii) are correct

6. Which of the following precautions need not be taken while using electric gadgets / appliances/circuit?

(a) We should never touch a lighted electric bulb connected to the mains.
(b) We should never experiment with the electric supply from the mains or a generator or an inverter.
(c) We should never use just any wire or strip of metal in place of a fuse.
(d) We should never turn the switch in ON position

7. The soft-iron core of an electromagnet loses its magnetism once the current passing through the electromagnetic coil stops because.

(a) Domains lose their alignment when the current is stopped
(b) Iron cannot hold alignment for longer time even when the current is passing through the coil
(c) Magnetic properties of iron are weak
(d) Domains inside the iron get aligned in north to south direction

8. A __ is used in torches.

(a) Generator
(b) Fuse
(c) Secondary cell
(d) Dry cell

9. An element measure the flowing an electric current is:

(a) voltmeter
(b) filament
(c) circuit
(d) ammeter

10. Electromagnet is used in

(a) Battery
(b) Dry cell
(c) Electric bell
(d) Fuse

11. The bulb glows only when ................. flows through it.

(a) Current
(b) Light
(c) Air
(d) Water

12. An element measure the potential difference between two points in an electric circuit is:

(a) voltmeter
(b) filament
(c) circuit
(d) ammeter

13. A device which prevents or allows the current to flow through it

(a) Motor
(b) Terminal
(c) Conductor
(d) Switch

14. Electric current has energy called:

(a) voltmeter
(b) filament
(c) electrical energy
(d) none of these

15. The metal which is poor conductor of electricity is

(a) Gold
(b) Iron
(c) Aluminium
(d) tungsten

16. The amount of heat produced in a wire depends on its material-

(a) Length
(b) Thickness
(c) Length and thickness
(d) None of these

17. If a piece of soft iron is placed inside the coil n number of turns and current is passed in the coil from a battery, what name is then given to the device so obtained ?

(a) spectrometer
(b) gravitometer
(c) barometer
(d) electromagnet

18. If the coil in a simple generator is wound around a soft iron core then:

(a) strength of magnetic field increases.
(b) current produced will be increased.
(c) voltage produced will be increased
(d) all

19. In a bulb there is a thin wire called

(a) filament
(b) coil
(c) element
(d) fuse wire

20. A glowing bulb becomes warm due to the

(a) heating effect of current
(b) magnetic effect of current
(c) chemical effect of current
(d) physical effect of current

21. Which of the following is being used in place of fuses?

(a) MCB
(b) Nichrome
(c) Filament
(d) Switch

22. When electric current passes through a wire, it behave like a

(a) battery
(b) magnet
(c) fuse
(d) compass needle

23. Fuse wire is generally made of

(a) tin and lead
(b) nickel and chromium
(c) nickel and copper
(d) chromium and silver

24. Coils of heating devices are made up of

(a) Mercury
(b) Nichrome
(c) Copper
(d) Tungsten

25. When electric current flows through a conductor, some amount of:

(a) electrical energy is converted into heat energy
(b) electrical energy is converted into mechanical energy
(c) mechanical energy is converted into electrical energy
(d) heat energy is converted into electrical energy

Answer:

1. Answer: (a) positive terminal of one cell is connected to the negative terminal of the next cell

Explanation: The positive terminal of one cell is connected to the negative terminal of the next cell. Such a combination is called a battery.

2. Answer: (c) Can be placed anywhere in the circuit

Explanation:  The key or Switch can be placed anywhere in the electric circuit.

3. Answer: (b) element

Explanation: An electric room heater or an electric heater used for cooking contains a coil of wire. The coil of wire used in electric heaters is called a heating element.

4. Answer: (b) ISI

Explanation: ISI mark is the mark necessary for appliance approval.

5. Answer: (b) (ii) and (iii) are correct

Explanation: When the switch is off, the circuit is in open position and current does not flow through the circuit as the circuit is not complete. So, the correct options are (ii), (iii).

6. Answer: (d) We should never turn the switch in ON position

Explanation: We should never turn the switch in ON position.

7. Answer: (a) Domains lose their alignment when the current is stopped

Explanation: As the current in coil flows due to electromagnetism, it behaves as magnet then the elementary magnets of soft iron core get attracted and on stopping current elementary magnets lose alignment.

8. Answer: (d) Dry cell

Explanation: A common dry cell used in torches consists of a rod surrounded by a chemical paste in a metal case.

9. Answer: (d) ammeter

Explanation: The ammeter is used to measure, the rate at which the electrons flow through the globes and the voltmeter measures the potential drop that is actually the loss in potential energy as the electricity moves through the filament.

10. Answer: (c) Electric bell

Explanation: An electric bell is a mechanical or electronic bell that functions by means of an electromagnet. When an electric current flows through the coils, the electromagnet creates a magnetic field which pulls the armature towards it, causing the hammer to strike the bell.

11. Answer: (a) Current

Explanation: The bulb glows only when current flows through the circuit and current heats the filament of bulb and bulb gives light.

12. Answer: (a) voltmeter

Explanation: The energy is transferred to the electrical components in a circuit when the charge carriers pass through them. We use a voltmeter to measure potential difference (or voltage). The potential difference (which is the same as voltage) is equal to the amount of current multiplied by the resistance.

13. Answer: (d) Switch

Explanation: A switch prevents or allows current to flow through it. It is a device used for making and breaking connections in an electric circuit. For example, when anyone presses the button (switch) for light/fan, with the completion of the circuit, the device starts to function.

14. Answer: (c) electrical energy

Explanation: Electrical energy is caused by moving electric charges called electrons. The faster the charges move, the more electrical energy they carry. As the charges that cause the energy are moving, electrical energy is a form of kinetic energy.

15. Answer: (d) tungsten

Explanation: Tungsten is a poor conductor of electricity even though it is a metal. But at high temperatures, it will conduct electricity. As discussed above, it has a high melting point. Therefore, high temperature doesn't have any bad effect on Tungsten.

16. Answer: (c) Length and thickness

Explanation: Amount of heat produced in wire = I²R 

Where R = Resistance of wire

I = Current through wire

As resistance of wire \(R\propto \frac{L}{A}\)

So heat produced depends on Length as well as thickness.        

17. Answer: (d) electromagnet

Explanation: A solenoid is a long coil containing a large number of close turns of insulated copper wire wound on a conducting or non-conducting material. In this case, we consider a coil wound on a soft iron bar called the core.When the circuit is closed by pressing the key, a steady current flow through such a device, the magnetic fields produced by the solenoid are similar to the magnetic field produced by a magnet and hence it is called as an Electromagnet.The strength of an electromagnet is related to factors stated below:

(i) Directly proportional to the number of turns in the coil.

(ii) Directly proportional to the current flowing in the coil. 

(iii) Inversely proportional to the length of air gap between the poles.

18. Answer: (d) all

Explanation: Voltage/current produced in a generator can be increased by: 

(a) Using a powerful electromagnet to make the magnetic field stronger in place of a permanent magnet.
(b) By winding the coil round a soft iron core to increase the strength of magnetic field.
(c) By using a coil with more turns.
(d) By rotating the coil faster.
(e) By using a coil with a larger area.

19. Answer: (a) filament

Explanation: An incandescent light bulb has a small thin wire with two bigger wires holding it up. This wire is called a filament. The filament is the part of the light bulb that produces light. Filaments in incandescent light bulbs are made of tungsten.

20. Answer: (a) heating effect of current

Explanation: Glowing electric bulbs becomes warm due to the heating effect of electric current. The current flowing through the filament of the bulb heats up the filament due to Joules heating and the bulb glows. The heat that is responsible for the production of light in the filament heats up the bulb.

21. Answer: (a) MCB

Explanation: These days MCBs (miniature circuit breakers) are used in place of electric fuses. They are switches which turn off automatically when current exceeds safe limit.

22. Answer: (b) magnet

Explanation: When an electric current flows through a wire, it behaves like a magnet. „ A current carrying coil of an insulated wire wrapped around a piece of iron is called an electromagnet. The electromagnets are also used to separate magnetic material from the junk.

23. Answer: (a) tin and lead

Explanation: A fuse is an automatic means of removing power from a faulty system.So, metals with low melting point and high resistance are used to make a fuse wire. Therefore, tin or tin-lead alloy whose melting point is low will be used in making fuse wire.

24. Answer: (b) Nichrome

Explanation: Most heating elements use Nichrome 80/20 (80% nickel, 20% chromium) wire, ribbon, or strip. Nichrome 80/20 is an ideal material, because it has relatively high resistance and forms an adherent layer of chromium oxide when it is heated for the first time. Material beneath this layer will not oxidize, preventing the wire from breaking or burning out.Hence, nichrome is used as heating elements.

25. Answer: (a) electrical energy is converted into heat energy

Explanation: A conductor allows the flow of electrons through itself that produces electric current. But conductors also resist the flow of electrons to some extent. When electron flow is restricted, some of the energy of electrons is converted to heat energy instead of electrical energy.

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