Question

Battery supplies 150w and 196w power to two resistors of 6 ohms and 4 ohms when they are connected separately to it. the internal resistance of the battery is

Answer 1

Let's write the formulae of power in terms of I and R

P = I²R

The 150 W, supplies 6 ohms

150 = I² × 6

6I² = 150

I² = 25

I = 5A

For the 196 W, 4 ohms

196 = I²4

I² = 49

I = 7 A

V = IR + Ir

Where r is the internal resistance.

We will have two equations for V :

V = 5 × 6 + 5r = 30 + 5r

V = 7 × 4 + 7r = 28 + 7r

Equating the two :

30 + 5r = 28 + 7r

2r = 2

r = 1

Answer :

1 ohm

Answer 2

Answer:

Explanation:

Let's write the formulae of power in terms of I and R

P = I²R

The 150 W, supplies 6 ohms

150 = I² × 6

6I² = 150

I² = 25

I = 5A

For the 196 W, 4 ohms

196 = I²4

I² = 49

I = 7 A

V = IR + Ir

Where r is the internal resistance.

We will have two equations for V :

V = 5 × 6 + 5r = 30 + 5r

V = 7 × 4 + 7r = 28 + 7r

Equating the two :

30 + 5r = 28 + 7r

2r = 2

r = 1

Answer :

1 ohm