Draw a schematic diagram of a circuit consisting of a battery of 3 cells of 2 V each, a combination of three resistors of 10 W, 20 W, and 30 W connected in parallel, a plug key, and an ammeter, all connected in series. Use this circuit to find the value of the following :(a) Current through each resistor.(b) Total current in the circuit.(c) Total effective resistance of the circuit.



Given:

Resistance, $R_1=10\Omega$

Resistance, $R_2=20\Omega$

Resistance, $R_3=30\Omega$

Number of cells $=3$

Voltage of each cell =2 V

Total volatgeof the battery, $V=2\times {3}=6V$

To find: (a) Current through each resistor.

               (b) Total current in the circuit.

               (c) Total effective resistance of the circuit.


Solution: (c) Total effective resistance of the circuit.

Here, all the resistance is given in parallel.

So, the total resistance is given by-

$\frac {1}{R_E}=\frac {1}{R_1}+\frac {1}{R_2}+\frac {1}{R_3}$

$\frac {1}{R_E}=\frac {1}{10}+\frac {1}{20}+\frac {1}{30}$

$\frac {1}{R_E}=\frac {6+3+2}{60}$

$\frac {1}{R_E}=\frac {11}{60}$

$\frac {1}{R_E}=\frac {11}{60}$

$R_E=\frac {60}{11}$

$R_E=5.45\Omega$

Thus, the total effective resistance, $R_E$ is 5.45 Ohm


Solution: (b) Total current in the circuit.

Now, we know that the total current in the circuit is given as-

$I=\frac {V}{R}$

Substituting the value of $V$ and $R$ we get-

$I=\frac {6}{5.45}$

$I=\frac {6\times {100}}{545}$

$I=\frac {600}{545}$
$I=1.1A$

Thus, the total current, $I$ in the circuit is 1.1 Ampere.


Solution: (a) Current through each resistor.

Let the current is $I_1$, $I_2$ and $I_3$ in the resistance $R_1$, $R_2$ and $R_3$.

We know that, in parallel combination, the voltage remains the same across each resistor.

Current $I$, in the circuit is given by the formula-

$I=\frac {V}{R}$

Substituting the given values we get-

$I_1=\frac {V}{R_1}\Rightarrow\frac {6}{10}\Rightarrow0.6A$

$I_1=\frac {V}{R_2}\Rightarrow\frac {6}{20}\Rightarrow0.3A$

$I_1=\frac {V}{R_3}\Rightarrow\frac {6}{30}\Rightarrow0.2A$

Thus, 

(a) Current through each resistor - 0.6A,  0.3A, 0.2A.

(b) Total current in the circuit - 1.1 Ampere.

(c) Total effective resistance of the circuit - 5.45 Ohm.

Updated on: 10-Oct-2022

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