Science : Electricity: Solved Example Problems with Answers, Solution

**Electricity - Science**

Solved Problems

1. Two bulbs are having the ratings as 60 W, 220 V and 40 W, 220 V respectively. Which one has a greater resistance?

Electric power P = V2/ R

For the same value of V, R is inversely proportional to P.

Therefore, lesser the power, greater the resistance

Hence, the bulb with 40 W, 220 V rating has a greater resistance.

2. Calculate the current and the resistance of a 100 W, 200 V electric bulb in an electric circuit

Power P = 100 W and Voltage V = 200 V

Power P = V I

3. In the circuit diagram given below, three resistors R1, R2 and R3 of 5 â„¦, 10 â„¦ and 20 â„¦ respectively are connected as shown. Calculate:

A) Current through each resistor

B) Total current in the circuit

C) Total resistance in the circuit

A) Since the resistors are connected in parallel, the potential difference across each resistor is same (i.e. V=10V)

Therefore, the current through R1 is,

B) Total current in the circuit, I = I1 + I2 + I3

= 2 + 1 + 0.5 = 3.5 A

4. Three resistors of 1 â„¦, 2 â„¦ and 4 â„¦ are connected in parallel in a circuit. If a 1 â„¦ resistor draws a current of 1 A, find the current through the other two resistors.

R1 = 1 â„¦, R2 = 2 â„¦, R3 = 4 â„¦ Current I1 = 1 A

The potential difference across the 1 â„¦ resistor = I1 R1 = 1 Ã— 1 = 1 V

Since, the resistors are connected in parallel in the circuit, the same potential difference will exist across the other resistors also.

So, the current in the 2 â„¦ resistor, V/R2= 1/2= 0.5 A

Similarly, the current in the 4 â„¦ resistor,

V/R2 = 1/4 = 0.25 A

Tags : Electricity | Science , 10th Science : Chapter 4 : Electricity

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10th Science : Chapter 4 : Electricity : Solved Problems | Electricity | Science

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