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 |
From NCERT
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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 |
 78%
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 |
 66%
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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A meter bridge is set up to determine unknown resistance x using a standard 10 Ω resistor. The galvanometer shows the null point when the tapping key is at a 52 cm mark. End corrections are 1 cm and 2 cm respectively for end A and B. Then the value of x is:

  

1.  10.2 Ω

2.  10.6 Ω

3.  10.8 Ω

3. 11.1 Ω

Subtopic:  Meter Bridge & Potentiometer |
 52%
From NCERT
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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 |
From NCERT
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