\(AB\) is a wire of uniform resistance. The galvanometer \(G\) shows no current when the length \(AC= 20~\text{cm}\) and \(CB = 80~\text{cm}\). The resistance \(R\) is equal to: 

1. \(2~\Omega\)
2. \(8~\Omega\)
3. \(20~\Omega\)
4. \(40~\Omega\)

The circuit shown here is used to compare the e.m.f. of two cells $E_1$ and $E_2(E_1>E_2)$. The null point is at C when the galvanometer is connected to E₁. When the galvanometer is connected to E₂, the null point will be 

(1) To the left of C

(2) To the right of C

(3) At C itself

(4) Nowhere on AB

In the Wheatstone's bridge (shown in the figure below) \(X=Y\) and \(A>B\). The direction of the current between \(a\) and \(b\) will be:

A resistance of 4 Ω and a wire of length 5 metres and resistance 5 Ω are joined in series and connected to a cell of e.m.f. 10 V and internal resistance 1 Ω. A parallel combination of two identical cells is balanced across 300 cm of the wire. The e.m.f. E of each cell is:

1. 1.5 V

2. 3.0 V

3. 0.67 V

4. 1.33 V

The resistance of an ideal voltmeter is 

(1) Zero

(2) Very low

(3) Very large

(4) Infinite

Constantan wire is used in making standard resistances because of its :

(1) Specific resistance is low

(2) Density is high

(3) Temperature coefficient of resistance is negligible

(4) Melting point is high

The net resistance of a voltmeter should be large to ensure that :

A potentiometer consists of a wire of length 4 m and resistance 10 Ω. It is connected to a cell of e.m.f. 2 V. The potential difference per unit length of the wire will be :

(1) 0.5 V/m

(2) 2 V/m

(3) 5 V/m

(4) 10 V/m

In the circuit shown $P\ne R$, the reading of the galvanometer is same with switch S open or closed. Then 

(1) $I_R=I_G$

(2) $I_P=I_G$

(3) $I_Q=I_G$

(4) $I_Q=I_R$

In the following Wheatstone bridge $P/Q=R/S$. If key K is closed, then the galvanometer will show deflection :

1. In left side

2. In right side

3. No deflection

4. none of the above