Two cells of emfs E1 and E2 are connected in series. Their internal resistances are r1 and r2 respectively. Compute the equivalent emf and equivalent internal resistance.

Education Journalist | Study Abroad Lead

When two cells of EMFs E₁ and E₂ are connected in series, their equivalent EMF is the algebraic sum of their EMFs. So, the equivalent EMF E will be:

E = E₁ + E₂

When two cells are connected in series, their internal resistances also add up to give the equivalent internal resistance r:

r = r₁ + r₂

Thus, the equivalent EMF is E₁ + E₂ and the equivalent internal resistance is r₁ + r₂.

Read More:

Important Topics
Carbon Resistor	Electric Charges and Fields MCQ	Wheatstone Bridge
Meter Bridge	NCERT Solutions Chapter 3 Current Electricity	Potentiometer
Types of Current	Cells, emf, Internal Resistance	Resistance Formula
Circuit Diagram	Resistor Colour Codes	Static Electricity

CBSE CLASS XII Related Questions

1.
Derive an expression for the capacitance of a parallel plate capacitor of plate area A and plate separation d with air present between the plates.
View Solution
2.
Two copper wires having their radii in the ratio of 3 : 2 are connected in series across a battery. Find the ratio of the drift velocities of the electrons in the wires.
View Solution
3.
An electric field $\vec{E}$ is established across the ends of a cylindrical conductor of length L and area of cross-section A. Discuss how electrons attain an average velocity, independent of time. Hence, obtain a relation between current in the conductor and this ‘average velocity’ of electrons.
View Solution
4.
Read the following paragraph and answer the questions that follow.
A p-type or n-type semiconductor can be converted into a p-n junction by doping it with suitable impurity. The motion of majority charge carriers causes diffusion current across the junction while the barrier electric field causes motion of minority carriers for drift current. In case of unbiased diode, the diffusion and drift currents are equal. This equilibrium is disturbed by the biasing batteries. Diodes, therefore, allow currents in one direction. This property of diode is used in making rectifiers.
5.
Two air-filled capacitors of capacitances $C_1$ and $C_2$ are connected in parallel with a dc battery. After the capacitors are fully charged, a slab of dielectric constant K is inserted between the plates of each capacitor. How will the (i) charge on each capacitor and (ii) energy stored in the capacitor affected after the slab is introduced.
View Solution
6.
An astronomical telescope consists of two converging lenses. One of them of large aperture and large focal length is called objective lens and the other one, of smaller focal length and smaller aperture is called the eyepiece. It is used to see distant objects which are not seen clearly with naked eyes. The image formed by the objective lens acts as an object for the eyepiece and the final image produced by the eyepiece is magnified.