Super Live session - Current Electricity

A potentiometer circuit is set up as shown. The potential gradient across the potentiometer wire is k volt/cm and the ammeter, present in the circuit, reads 1.0 A when the two-way key is switched off. The balance points, when the key between the terminals (i) 1 and 2 (ii) 1 and 3, is plugged in, are found to be at lengths $l_{1} c m$ and $l_{2} c m$ respectively. The magnitudes, of the resistors R and X, in ohm, are then, equal, respectively, to

1. $k (l_{2} - l_{1}) a n d k l_{2}$
2. $k l_{1} a n d k (l_{2} - l_{1})$
3. $k (l_{2} - l_{1}) a n d k l_{1}$
4. $k l_{1} a n d k l_{2}$

The resistance in the two arms of the balanced meter bridge as shown in figure are 5 and R, respectively. When the resistance R is shunted with an equal resistance, the new balance point is at 1.6l₁. The resistance 'R' is :

1. 10
2. 15
3. 20
4. 25

Six similar bulbs are connected as shown in the figure with a DC source of emf E and zero internal resistance.
The ratio of power consumption by the bulbs when (i) all are glowing and (ii) in the situation when two from section A and one from section B are glowing, will be:

1. 2: 1
2. 4: 9
3. 9: 4
4. 1: 2

See the electrical circuit shown in this figure. Which of the following equations is a correct equation for it?

1.

ε_{1} - (i_{1} + i_{2}) R - i_{1} r_{1} = 0

ε_{2} - i_{2} r_{2} - ε_{1} - i_{1} r_{1} = 0

- ε_{2} - (i_{1} + i_{2}) R + i_{2} r_{2} = 0

ε_{1} - (i_{1} + i_{2}) R + i_{1} r_{1} = 0

A wire of resistance 4Ω is stretched to twice its original length. The resistance of stretched wire would be :
1. 4Ω
2. 8Ω
3. 16Ω
4. 2Ω

A filament bulb (500 W, 100 V) is to be used in a 230 V main supply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W. The value of R is :
1. 230 $Ω$
2. 46 $Ω$
3. 26 $Ω$
4. 13 $Ω$

A potentiometer wire has length 4 m and resistance 8

Ω

. The resistance that must be connected in series with the wire and an accumulator of emf 2V, so as to get a potential gradient 1 mV per cm on the wire is
1. 32

Ω

2. 40

Ω

3. 44

Ω

4. 48

Ω

In the circuit shown, if a conducting wire is connected between points A and B, the current in this wire will: (All resistance given in ohms)

1. flow from A to B
2. flow in the direction which will be decided by the value of V
3. be zero
4. flow from B to A

Across a metallic conductor of non-uniform cross-section, a constant potential difference is applied. The quantity which remains constant along the conductor is :
1. current density
2. current
3. drift velocity
4. electric field

10.

A carbon resistor of (47 ± 4.7) kΩ is to be marked with rings of different colours for its identification. The colour code sequence will be:
1. Violet - Yellow - Orange - Silver
2. Yellow - Violet - Orange - Silver
3. Yellow - Green - Violet - Gold
4. Green - Orange - Violet - Gold

11.

The charge following through a resistance R varies with time t as Q = at-bt², where a and b are positive constants. The total heat produced in R is:
1.

\frac{a^{3} R}{3 b}

\frac{a^{3} R}{2 b}

\frac{a^{3} R}{b}

\frac{a^{3} R}{6 b}

12.

A student measures the terminal potential difference (V) of a cell (of emf

ε

and internal resistance r) as a function of the current (I) flowing through it. The slope and intercept of the graph between V and I, respectively, equal to :
1. E and -r
2. -r and E
3. r and -E
4. -E and r

13.

In the given circuit, with a steady current, the potential drop across the capacitor must be :

(1) V
(2) V / 2
(3) V / 3
(4) 2V / 3

14.

In the circuit shown in the figure, the current through :

(1) The 3Ω resistor is 0.50A
(2) The 3Ω resistor is 0.25 A
(3) The 4Ω resistor is 0.50A
(4) The 4Ω resistor is 0.25 A

15.

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

(1) 4.5 A
(2) 6.0 A
(3) 3.0 A
(4) Zero

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