In the given circuit of below the cell P has an e.m.f. 1.5V and an unknown internal resistance r while the cell Q has an e.m.f. 2.0V …

Jamb 1979

In the given circuit of below the cell P has an e.m.f. 1.5V and an unknown internal resistance r while the cell Q has an e.m.f. 2.0V and an internal resistance of 1ohm. If the ammeter reads 50mA, then r is equal to A. 0.5 ohm B.0.62 ohm C. 1.0 ohm D. 2.0 ohms E. 3.0 ohms. 

In the given circuit of below the cell P has an e.m.f. 1.5V and an unknown internal resistance r while the cell Q has an e.m.f. 2.0V and an internal resistance of 1ohm. If the ammeter reads 50mA, then r is equal to

ANSWER: Option D

EXPLANATION: Since the cells are connected -ve to -ve, the total emf will be 2.0V – 1.5V = 0.5V

emf = I(R + r + r2)

Where; emf is the resultant Volts the two cells gives

I is the current in the circuit

r is the internal resistance of the first cell

r2 is the internal resistance of the second cell

0.5 = 50 × 10⁻³ (7 + r + 1)

0.5 = 50 × 10⁻³ (8 + r)

Now, solve for r to get your answer!

Previous       Next

Or click here to choose! 

Of course, your opinion(s) and suggestion(s) is/are welcome. In case, you have any, kindly use our comment box.

If you have any questions, you can also drop them in the comment section.

If you find this post beneficial, feel free to use the share button to share with friends.

Follow us on our Facebook page!

Leave a Comment

Your email address will not be published.