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NEET - Physics Current Electricity Practice Q & A

23459.Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is 0.5 Ω. The power loss in the wire is
19.2 W
19.2 kW
19.2 J
12.2 kW
23460.The thermistors are usually made of:
metals with low temperature coefficient of resistivity
metals with high temperature coefficient of resistivity
metal oxides with high temperature coefficient of resistivity
semiconducting materials having low temperature coefficient of resistivity
23461.A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected across the given cell, has values of
(i) Infinity
(ii) 9.5 Ω,
the balancing lengths on the potentiometer wire are found to be 3 m and 2.85 m, respectively. The value of internal resistance of the cell is
0.25 Ω
0.95 Ω
0.5 Ω
0.75 Ω
23462.In a potentiometer experiment, the balancing length with a cell is 240 cm. On shunting the cell with a resistance of 2 Ω, the balancing length becomes 120 cm. The internal resistance of the cell is
1 Ω
0.5 Ω
4 Ω
2 Ω
23463.The thermo emf of a thermocouple varies with the temperature θ of the hot junction as E = aθ + bq2 (in volts) where the ratio a/b is 700°C. If the cold junction is kept at 0°C, then the neutral temperature of the thermocouple is:
700°C
350°C
1400°C
no neutral temperature is possible for this thermocouple
23464.The supply voltage to a room is 120 V. The resistance of the lead wires is 6 Ω. A 60 W bulb is already switched on. What is the decrease of voltage across the bulb, when a 240 W heater is switched on in parallel to the bulb?
Zero volt
2.9 volt
13.3 volt
10.04 volt
23465.Two large vertical and parallel metal plates having a separation of 1 cm are connected to a DC voltage source of potential difference X. A proton is released at rest midway between the two plates. It is found to move at 45° to the vertical JUST after release. Then X is nearly
1 × 10–5 V
1 × 10–7 V
1 × 10–9 V
1 × 10–10 V
23466.Two heating coils of resistances 10 Ω and 20 Ω are connected in parallel and connected to a battery of emf 10 V and internal resistance 1 Ω. The power consumed by them are in the ratio
1: 4
1: 3
2: 1
4: 1
23467.In an LCR circuit as shown below both switches are open initially. Now switch S1 is closed, S2 kept open (q is charge on the capacitor and τ = RC is Capacitive time constant). Which of the following statement is correct? LCR circuit with open switches
Work done by the battery is half of the energy dissipated in the resistor
At t = τ, q = CV/2
At t = 2τ, q = CV(1 – e–2)
At t = τ/2, q = CV(1 – e–1)
23468.Three resistances 2 Ω, 3 Ω and 4 Ω are connected in parallel. The ratio of currents passing through them when a potential difference is applied across its ends will be
5 : 4 : 3
6 : 3 : 2
4 : 3 : 2
6 : 4 : 3
23469.If a wire is stretched to make it 0.1% longer, its resistance will
increase by 0.05%
increase by 0.2%
decrease by 0.2%
decrease by 0.05%
23470.A potentiometer wire of length 10 m is connected in series with a battery. The e.m.f. of a cell balances against 250 cm length of wire. If length of potentiometer wire is increased by 1 m, the new balancing length of wire will be
2.00 m
2.25 m
2.50 m
2.75 m
23471.In potentiometer experiment, null point is obtained at a particular point for a cell on potentiometer wire x cm long. If the length of the potentiometer wire is increased without changing the cell, the balancing length will (Driving source is not changed)
increase
decrease
not change
becomes zero
23472.The resistance in the two arms of the meter bridge are 5 Ω and R Ω, respectively. When the resistance R is shunted with an equal resistance, the new balance points is at 1.6 l1. The resistance R is:
 resistance in meter bridge
10 Ω
15 Ω
20 Ω
25 Ω
23473.The resistances in left and right gap of a meter bridge are 20 Ω and 30 Ω respectively. When the resistance in the left gap is reduced to half its value, the balance point shifts by
15 cm to the right
15 cm to the left
20 cm to the right
20 cm to the left
23474.A 220 volt, 1000 watt bulb is connected across a 110 volt mains supply. The power consumed will be
1000 watt
750 watt
500 watt
250 watt
23475.Shown in the figure below is a meter–bridge set up with null deflection in the galvanometer.
meter–bridge with null deflection galvanometer
The value of the unknown resistor R is
220 Ω
110 Ω
55 Ω
13.75 Ω
23476.In the circuit shown, the current in the 1Ω resistor is
1 ohm resistor circuit
0 A
1.3 A, from P to Q
0.13 A, from Q to P
0.13 A, from P to Q
23477.A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf’s is
3 : 4
3 : 2
5 : 1
5 : 4
23478.Two electric bulbs marked 25 W – 220 V and 100 W – 220 V are connected in series to a 440 V supply. Which of the bulbs will fuse?
both
100 W
25 W
neither
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