Cells In Series

Question

Four identical cells, each of emf 1.5 volts and internal resistance 0.2 ohm, are connected in series to power a small torch, so what is the net emf and total internal resistance?

RankGuru · Accepted Answer

When identical cells are joined in series, their emfs add up and their internal resistances also add up, since the same current passes through each cell in turn, a rule explained in NCERT Class 12, Chapter 3 (Current Electricity). The net emf is $n\varepsilon = 4 	imes 1.5 = 6$ V, and the total internal resistance is $nr = 4 	imes 0.2 = 0.8$ ohm. Series stacking is chosen when a higher driving voltage is needed. The option 1.5 V and 0.05 ohm instead describes a parallel connection of identical cells, where the emf stays that of one cell and the internal resistance drops to $r/n$. The option 6 V and 0.05 ohm incorrectly mixes the series emf with the parallel internal resistance, combining rules from two different arrangements. The option 1.5 V and 0.8 ohm wrongly keeps a single cell's emf while correctly adding the resistances, an inconsistent pairing. A consistency check confirms the result: four 1.5 V cells stacked in a torch sensibly give 6 V, and internal resistances placed in series add just like ordinary series resistors, so 0.8 ohm is the correct total and the emf and resistance both scale by the same factor of four.

Cells In Series

Select the correct option:

🔒 Solution Hidden from View

More current electricity Practice Questions

Engineers relate the current density inside a conductor to the local electric field through the mate...

Three identical cells, each with internal resistance 0.6 ohm, are connected in parallel to reduce th...

A battery of emf 12 volts and internal resistance 3 ohm drives a variable load resistor, so for what...

An electric heater rated to carry 5 amperes operates across a 220 volt mains supply in a kitchen, so...

Current passes through a 20 ohm resistor at 2 amperes for 5 minutes in a demonstration, so how much ...

While measuring a battery on a test bench, its terminal voltage drops from 12 volts on open circuit ...

A cell of emf 6 volts and internal resistance 0.5 ohm is connected to an external resistor of 2.5 oh...

Two resistors of 6 ohm and 3 ohm are wired side by side between the same two nodes of a circuit, so ...

At a junction in a network, currents of 5 A and 3 A enter while currents of 4 A and I leave through ...

A potentiometer is often preferred over a voltmeter for measuring the emf of a cell accurately, so w...

In a balanced Wheatstone bridge the galvanometer shows no deflection, so which relation among the fo...

In a meter bridge the balance point is found at 40 cm from one end while the known resistance in the...

About This Question

Solution