A 100 W bulb designed to operate on 100 V is to be connected across a 500 V source. Find the resistance to be put in series so that bulb consumes 100 W only.

(1) 100 Ω

(2) 500 Ω

(3) 400 Ω

(4) 300 Ω

Subtopic:  Heating Effects of Current |
 67%
From NCERT
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A torch bulb rated 4.5 W, 1.5 V is connected as shown in the figure below. The emf of the cell needed to make the bulb glow at full intensity is:

1. 4.5 V

2. 1.5 V

3. 2.67 V

4. 13.5 V

Subtopic:  Heating Effects of Current |
From NCERT
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The reading of an ideal voltmeter in the circuit shown is:

    

1. \(0.6\) V 2. \(0\)
3. \(0.5\) V 4. \(0.4\) V
Subtopic:  Kirchoff's Voltage Law |
From NCERT
NEET - 2019
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The metre bridge shown is in a balanced position with \(\frac{P}{Q} = \frac{l_1}{l_2}\). If we now interchange the position of the galvanometer and the cell, will the bridge work? If yes, what will be the balanced condition?

    
1. Yes, \(\frac{P}{Q}=\frac{l_1-l_2}{l_1+l_2}\)
2. No, no null point
3. Yes, \(\frac{P}{Q}= \frac{l_2}{l_1}\)
4. Yes, \(\frac{P}{Q}= \frac{l_1}{l_2}\)

Subtopic:  Meter Bridge & Potentiometer |
 62%
From NCERT
NEET - 2019
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A factory is served by a 220 V supply line. In a circuit protected  by a fuse marked 10 A, the maximum number of 100 W lamps in parallel that can be turned on is :

1. 11 

2. 22

3. 33

4. 66

Subtopic:  Heating Effects of Current |
 85%
From NCERT
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Figure 7.44 shows three similar lamps L1, L2 and L3 connected across a power supply. If the lamp L3 fuses, how will the light emitted by L1 and L2 change?

(1) no change

(2) brilliance of both L1 decreases and that of L2 increases

(3) brilliance of both L1 and L2 increases

(4) brilliance of both L1 and L2 decreases

Subtopic:  Heating Effects of Current |
 57%
From NCERT
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Two electric bulbs A and B are rated 60 W and 100 W, respectively. If they are connected in parallel to the same source, then,

(1) both the bulbs draw the same current

(2) bulb A draws more current than bulb B

(3) bulb B draws more current than bulb A

(4) currents drawn in the bulbs are in the ratio of their resistances

Subtopic:  Heating Effects of Current |
 73%
From NCERT
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The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use?

(1) 14,000 Ω

(2) 400 Ω

(3) 40 Ω

(4) 4 Ω

Subtopic:  Heating Effects of Current |
 52%
From NCERT
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Three bulbs of 40 W, 60 W, and 100 W are connected in series with a 240 V source. Then,

(1) The potential difference will be the maximum across the 40 W bulb.

(2) The current will be the maximum in 100 W bulb.

(3) The resistance of the 40 W bulb is the minimum.

(4) The current through the 60 W bulb will be 0.1 A.

Subtopic:  Heating Effects of Current |
From NCERT
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A wire, when connected to a 220 V mains supply, has power dissipation P1. Now, the wire is cut into two equal pieces, which are connected in parallel to the same supply. Power dissipation in this case is P2. Then P2:P1  is :

(1) 1

(2) 4

(3) 2

(4) 3

Subtopic:  Heating Effects of Current |
 66%
From NCERT
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