NEET Physics Current Electricity Questions Solved

BOARD

(a) (i) State the principle on which a potentiometer works. How can a given potentiometer be made more sensitive?

(ii) In the graph shown below for two potentiometers, state with reason which of the two potentiometers, A or B, is more sensitive.

(b) Two metallic wires, ${P}_{1}$ and ${P}_{2}$ of the same material and same length but different cross - sectional of emf. Find the ratio of the drift velocities of free electrons in the two wires when they are connected (i) in series, and (ii) in parallel.                                                      5 marks

(a) (i) The potential difference across any length of wire is directly proportional to the length provided current and area of cross section are constant i.e., E(l) = $\varnothing l$ where $\varnothing$is the potential drop per unit length.                                                                                                       1mark

It can be made more sensitive by decreasing current in the main circuit / decreasing potential gradient / increasing resistance put in series with the potentiometer wire.                   $1}{2}$mark

(ii) Potentiometer B                                                                                                $1}{2}$mark

Has smaller value of $V}{l}$  (slope / potential gradient).                                           $1}{2}$mark

(b) In series, the current remains the same.                                                              $1}{2}$mark

I =ne${A}_{1}{V}_{d1}=ne{A}_{2}{V}_{d2}$                                                                                             $1}{2}$mark

$\therefore \frac{{V}_{d1}}{{V}_{d2}}=\frac{{A}_{2}}{{A}_{1}}$                                                                                                     $1}{2}$mark

In parallel potential difference is same but currents are different.

$V={I}_{1}{R}_{1}=ne{A}_{1}{V}_{d1}\frac{\rho l}{{A}_{1}}=ne\rho {V}_{d1}l$                                                                            $1}{2}$mark

Similarly, $V={I}_{2}{R}_{2}=ne\rho {V}_{d2}l$                                                                                    $1}{2}$mark

Difficulty Level:

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