If a resistance coil is made by joining in parallel two resistances each of 20Ω. An emf of 2V is applied across this coil for 100 seconds. The heat produced in the coil is

(1) 20 J

(2) 10 J

(3) 40 J

(4) 80 J

Subtopic:  Heating Effects of Current |
 69%
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Which of the following graph correctly represents the variation of mobility μ of electrons with applied electric field (E) in a metallic conductor?

1. 2.
3. 4.
Subtopic:  Current & Current Density |
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If I be the current limit of a fuse wire of length l and radius r, then select the appropriate relation

(1) I α l

(2) I α r2

(3) I α l0

(4) I α r0

Subtopic:  Heating Effects of Current |
From NCERT
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The resistance of platinum wire at 0°C is 22.05 Ω and at 100°C it becomes 22.70 Ω. When the wire is heated to a temperature of t°C the resistance of wire becomes 24.91Ω. The value of t is 

1.  220

2.  440

3.  310

4.  550

Subtopic:  Derivation of Ohm's Law |
 63%
From NCERT
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The sensitivity of a potentiometer can be increased by

1.  increasing the potential gradient

2.  decreasing the length of potentiometer wire

3.  decreasing the current in the potentiometer wire

4.  all of these

Subtopic:  Meter Bridge & Potentiometer |
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In the circuit shown in  figure if power dissipated in 9Ω resistor is 144W, then potential difference across 3.6Ω resistor will be

1.  36V

2.  18V

3.  9V

4.  Zero

Subtopic:  Heating Effects of Current |
 65%
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A current of 1 mA is flowing through a copper wire. How many electrons will pass a given point in one second  e = 1.6 × 10-19 Coulomb

1.  6.25 × 1019  

2.  6.25 × 1015  

3.  6.25 × 1031  

4.  6.25 × 108

Subtopic:  Current & Current Density |
 79%
From NCERT
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The drift velocity of free electrons in a conductor is \(v\) when a current \(i\) is flowing in it. If both the radius and current are doubled, then the drift velocity will be:
1.  \(v\)
2. \(\frac{v}{2}\)
3. \(\frac{v}{4}\)
4. \(\frac{v}{8}\)

Subtopic:  Current & Current Density |
 73%
From NCERT
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A battery has e.m.f. 4 V and internal resistance r. When this battery is connected to an external resistance of 2 ohm, a current of 1 ampere flows in the circuit. How much current will flow if the terminals of the battery are connected directly?

1. 1 A 2. 2 A
3. 4 A 4. Infinite
Subtopic:  EMF & Terminal Voltage |
 67%
From NCERT
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The current I as shown in the circuit will be:

                 

1.  10 A

2.  203 A 

3.  23 A  

4.  53 A

Subtopic:  Combination of Resistors |
 61%
From NCERT
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