Question

When n number identical cell of emf E and internal resistance is connected in series, the net internal resistance of the system will be

• A. $\frac{nEr}{1+E}$
• B. $n^{2}r$
• C. $nr$
• D. $n/r$

Answer 1

The correct option is C $nr$

It is a common fact that when current flows the circuit, connected with a magnetic compass, the magnetic needle in the compass will show deflection due to the magnetic effect of the current. Magnetic lines of forces are created around the coil of wire and this caused the needle to deflect according to the direction of the current.
In this case, when the number of cells in the circuit is increased, the current through the circuit is also increased. This is because, the increase in cells indicates more current in the circuit.
Hence, as the current in the circuit is increased, the deflection in the magnetic compass also increase further.