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**Lakhmir Singh Physics Class 10 Solutions ****Page No:40**

**Question 24:****In the circuit diagram given below, three resistors R _{1,} R_{2}, and R_{3} of 5 Î©, 10 Î© and 30 Î©, respectively are connected as shown.**

**Calculate : (a) current through each resistor. (b) total current in the circuit. (c) total resistance in the circuit.**

V = 12V

R_{1}, R_{2} and R_{3} are connected in parallel.

(a) Current through R_{1} = V/R_{1} = 12/5 = 2.4 A

Current through R_{2} = V/R_{2} = 12/10 = 1.2 A

Current through R_{3} = V/R_{2} = 12/30 = 0.4A

(b) Total current in the circuit = 2.4 + 1.2 + 0.4 = 4 A

(c) Total resistance in the circuit=R

1/R = 1/R_{1}+ 1/R_{2}+ 1/R_{3}

1/R = 1/5 + 1/10 + 1/30

1/R = 10/30

R = 3 ohm

**Question 25:****A p.d. of 4 V is applied to two resistors of 6 Î© and 2 Î© connected in series. Calculate : (a) the combined resistance (b) the current flowing (c) the p.d. across the 6 Î© resistor**

**Solution :**

V = 4V.

R_{1 }= 6 ohm. R_{2} = 8 ohm (in series)

(a) Combined resistance. R = R_{1} + R_{2} = 6+2 = 8ohm

(b) Current flowing. I = V/R = 4/8=0.5amp

(c) p.d. across 6ohm resistor = I x R_{1} = 0.5 x 6 = 3 V

**Question 26:****A p.d. of 6 V is applied to two resistors of 3 Î© and 6 Î© connected in parallel. Calculate : (a) the combined resistance (b) the current flowing in the main circuit (c) the current flowing in the 3 Î© resistor.**

V = 6V

R1= 3 ohm. R2 = 6 ohm (in parallel)

(a) Combined resistance.

1/R = 1/R_{1}+ 1/R_{2}

1/R = 1/3 + 1/6 = 3/6 = 1/2

R = 2 ohm

(b) Current flowing in the main circuit. I = V/R = 6/2 = 3 A

(c) Current flowing in 3 ohm resistor = V/R_{1}= 6/3 = 2 A

**Question 27:****In the circuit shown below, the voltmeter reads 10 V.**

**(a) What is the combined resistance ? (b) What current flows ? (c) What is the p.d. across 2 Î© resistor ? (d) What is the p.d. across 3 Î© resistor ?**

**Solution :**

(c) p.d. across 2Î© resistor=1 xR_{1 }= 2 x 2 = 4V

(d) p.d. across 3Î© resistor=1 x R_{2} = 2 x 3 = 6V

**Question 28:****In the circuit given below :**

**(a) What is the combined resistance ? (b) What is the p.d. across the combined resistance ? (c) What is the p.d. across the 3 Î© resistor ? (d) What is the current in the 3 Î© resistor ? (e) What is the current in the 6 Î© resistor ?**

Total current flowing through circuit. I = 6 A

R_{1} = 3 ohm. R_{2} = 6 ohm

(a) Combined resistance R is

1/R = 1/3+1/6

1/R = 3/6

R = 2ohms

(b) p.d. across the combined resistance = IR = 6 x 2 = 12 V

(c) p.d. across the 3 ohm resistor = p.d. across the combined resistance = 12 V

(d) Current flowing through the 3 ohm resistor = V/R_{1} = 12/3 = 4 A

(e) Current flowing through the 6 ohm resistor = V/R_{2} = 12/6 = 2 A

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