Current Electricity - Live Session

1.

If each resistance in the figure is of 9 $Ω$ then reading of ammeter is

1. 5 A
2. 8 A
3. 2 A
4. 9 A

2.

In the circuit shown, the point 'B' is earthed. The potential at the point 'A' is

1. 14 V
2. 24 V
3. 26 V
4. 50 V

3.

In the figure, the value of resistors to be connected between C and D so that the resistance of the entire circuit between A and B does not change with the number of elementary sets used is

1. R
2. R $(\sqrt{3} - 1)$
3. 3 R
4. R $(\sqrt{3} + 1)$

4.

Find the equivalent resistance between the points a and b

1. 2 $Ω$
2. 4 $Ω$
3. 8 $Ω$
4. 16 $Ω$

5.

In an electrical cable, there is a single wire of radius 9 mm of copper. Its resistance is 5 $Ω$ . the cable is replaced by 6 different insulated copper wires, the radius of each wire is 3mm. Now the total resistance of the cable will be
1. 7.5 $Ω$
2. 45 $Ω$
3. 90 $Ω$
4. 270 $Ω$

6.

As the switch S is closed in the circuit shown in figure, current passed through it is

1. 4.5 A
2. 6.0 A
3. 3.0 A
4. zero

7.

If each of the resistance of hte network shown in the figure is R, the equivalent resistance between A and B is

1. 5 R
2. 3 R
3. R
4. R/2

8.

Consider four circuits shown in the figure below. In which circuit power dissipated is greatest (Neglect the internal resistance of the power supply)
1.
2.
3.
4.

9.

The n rows each containing m cells in series are joined in parallel. The maximum current is taken fro this combination across an external resistance of 3 $Ω$ resistance. If the total number of cells used are 24 and internal resistance of each cell is 0.5 $Ω$ then
1. m = 8, n = 3
2. m = 6, n = 4
3. m = 12, n = 2
4. m = 2, n = 12

10.

A cell of constant e.m.f first connected to a resistance R₁ and then conncted to a resistance R₂. If power delivered in both cases is then the internet resistance of the cell is
(1) $\sqrt{R_{1} R_{2}}$
(2) $\sqrt{\frac{R_{1}}{R_{2}}}$
(3) $\frac{R_{1} - R_{2}}{2}$
(4) $\frac{R_{1} + R_{2}}{2}$

11.

In the figure shown, the capacity of the condenser C is 2 $μ$ F. The current is 2 $Ω$ resistor is

(1) 9 A
(2) 0.9 A
(3) $\frac{1}{9} A$
(4) $\frac{1}{0.9} A$

12.

In the circuit shown, the value of each of the resistances is $r$. The equivalent resistance of the circuit between terminals $A$ and $B$ will be:

1.	$\dfrac{4r}{3}$	2.	$\dfrac{3r}{2}$
3.	$\dfrac{r}{3}$	4.	$\dfrac{8r}{7}$

13.

Two cells of equal e.m.f. and of internal resistances $r_{1}$ and $r_{2} (r_{1} > r_{2})$ are connected in series. On connecting this combination to an exyernal resistance R, it is observed that the potential difference across the first cell becomes zero. The value of R will be
$(1) r_{1} + r_{2}$
$(2) r_{1} - r_{2}$
$(3) \frac{r_{1} + r_{2}}{2}$
$(4) \frac{r_{1} - r_{2}}{2}$

14.

The effective resistance between points P and Q of the electrical circuit shown in the figure is

1. 2 Rr / (R + r)
2. 8R (R + r) / (3R + r)
3. 2r + 4 R
4. 5 R/2 + 2r

15.

A wire of resistor R is bent into a circular ring of radius r. Equivalent resistance between two points X and Y on its circumference, when angle XOY is $α$ , can be given by

1. $\frac{Rα}{4 π^{2}} (2 π - α)$
2. $\frac{R}{2 π} (2 π - α)$
3. $R (2 π - α)$
4. $\frac{4 π}{R α} (2 π - α)$

16.

In the following circuit a $10 m$ long potentiometer wire with resistance 1.2 ohm/m, a resistance $R 1 $ and an accumulator of emf $2 V$ are connected in series. When the emf of thermocouple is $2.4 m V then the deflection in$ galvanometer is zero. The current supplied by the accumulator will be

1. $4 \times 10^{- 4} A$
2. $8 \times 10^{- 4} A$
3. $4 \times 10^{- 3} A$
4. $8 \times 10^{- 3} A$

17.

In the following star circuit diagram (figure), the equivalent resistance between the point A and H will be

1. 1.944r
2. o.973r
3. o.486r
4. o.23r

18.

The V-i graph for a conductor at temperature $T_{1}$ and $T_{2}$ are shown in the figure. ( $T_{2}$ - $T_{1}$ ) is proportional to

(1) cos 2 $θ$
(2) sin $θ$
(3) cot 2 $θ$
(4) tan $θ$

19.

A resistance of 4 $Ω$ and a wire of length 5 meters and resistance 5 $Ω$ are joined in series and connected to 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

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1.	\(\dfrac{4r}{3}\)	2.	\(\dfrac{3r}{2}\)
3.	\(\dfrac{r}{3}\)	4.	\(\dfrac{8r}{7}\)

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