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 |
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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 |
 62%
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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:  Colour Coding of Resistors (OLD 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 |
 64%
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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. \(\dfrac{v}{2}\)
3. \(\dfrac{v}{4}\) 4. \(\dfrac{v}{8}\)
Subtopic:  Current & Current Density |
 73%
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A battery has emf \(4\) 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%
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The current \(I\) as shown in the circuit will be:

1. \(10~\text{A}\) 2. \(\dfrac{20}{3}~\text{A}\)
3. \(\dfrac{2}{3}~\text{A}\) 4. \(\dfrac{5}{3}~\text{A}\)
Subtopic:  Combination of Resistors |
 61%
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A meter bridge is set up to determine unknown resistance \(x\) using a standard \(10~\Omega\) 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. \(10.2~\Omega\)
2. \(10.6~\Omega\)
3. \(10.8~\Omega\)
4. \(11.1~\Omega\)

Subtopic:  Meter Bridge & Potentiometer |
 52%
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Which of the following graph correctly represents the variation of mobility \((\mu)\) of electrons with applied electric field \((E)\) in a metallic conductor?

1.   2.
3. 4.
Subtopic:  Current & Current Density |
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