In the poteniometer experiement shown in figure, the null point length is `l`. Choose the correct options given below

Options

A. If jockey `J` is shifted towards right l will increse
B. if value of `E_1` is increased l is decreased
C. if valued of `E_2` is incresed l in increased
D. if switched S is closed l will decrease

Answer

A, B, C, D

Explanation

If switch `S` is open
`i_1lamdal=E_2`
where `i_1=` current in upper circuit and `lamda` is resistance per unit length of potentiometer wire.
`:.` Null point length `l=E_2/(i_1lamda)`
a. If jockey is shifted towards right, resitance in upper circuit will increase. So, current `i_1` will decrease. Hence l will increase.
b. If `E_1` isincreased `i_1` will also increase. So, l will decrease.
c. `lpropE_2`
d. If switch is closed, then null point will be obtained corresponding to
`V_2=E_2-i_2r_2`
which is less than `E_2`. Hence null point length will decrease.