1.

A p.d of 6V is applied to two resistors of 3Ω and 6Ω connected in parallel . Calculate (i) equivalent resistance (ii) total current (ii) The current flowing in the 3Ω resistor .

Answer»

Solution :

Given:

✏ Two resistors of resistance 3Ω and 6Ω are CONNECTED in parallel with p.d. 6V

To Find:

  • Equivalent resistance
  • Total current flow in circuit
  • Current flow in 3Ω resistor

Formula:

FORMULA of eq. resistance in parallel connection is given by...

\bigstar \:  \boxed{ \tt{ \large{ \pink{R_{eq} =  \dfrac{R_1 \times R_2}{R_1 + R_2}}}}} \:  \bigstar

✏ As per ohm's law, RELATION between potential difference, resistance and current is given by...

\bigstar \:  \boxed{ \tt{ \large{ \purple{V = I \times R}}}} \:  \bigstar

Calculation:

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  • Equivalent resistance

\dashrightarrow \sf \: R_{eq} =  \dfrac{3 \times 6}{3 + 6}  \\  \\  \dashrightarrow \sf \: R_{eq} =  \dfrac{18}{9}  \\  \\  \dashrightarrow \:  \boxed{ \tt{ \red{\large{R_{eq} = 2 \:  \Omega}}}} \:  \orange{ \bigstar}

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  • Total current flow

\implies \sf \: V = I_{net} \times R_{eq} \\  \\  \implies \sf \: 6 = I_{net} \times 2 \\  \\  \implies \sf \: I_{net} =  \dfrac{6}{2}  \\  \\  \implies \:  \boxed{ \tt{\large{ \green{I_{net} = 3 \: A}}}} \:  \orange{ \bigstar}

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  • Current flow in 3Ω resistor

\rightarrowtail \sf \: V = I \times R \\  \\  \rightarrowtail \sf \: 6 = I \times 3 \\  \\  \rightarrowtail \sf \: I =  \dfrac{6}{3}  \\  \\  \rightarrowtail \:  \boxed{ \tt{ \large{\blue{I = 2 \: A}}}} \:  \orange{ \bigstar}

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Additional information:

  • Ohm's law is not APPLICABLE for semi-conductor devices.
  • Potential difference REMAINS same across all resistors in parallel connection.
  • Current is fundamental quantity.


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