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 |
 67%
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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 |
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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%
From NCERT
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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%
From NCERT
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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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A galvanometer of resistance \(240~\Omega\) allows only \(4\%\) of the main current after connecting a shunt resistance. What is the value of shunt resistance?
1. \(10~\Omega\)
2. \(20~\Omega\)
3. \(8~\Omega\)
4. \(5~\Omega\)

Subtopic:  Conversion to Ammeter & Voltmeter |
 75%
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The current in a wire varies with time according to the relation \(i = (3+2t)~\text{A}\). The amount of charge passing a cross section of the wire in the time interval \(t=0\) to \(t = 4.0~\text{s}\)  would be: (where \(t\) is time in seconds)
1. \(28\) C 2. \(30.5\) C
3. \(8\) C 4. \(82\) C
Subtopic:  Current & Current Density |
 85%
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The resistivity of iron is 1 × 10–7 ohm m. The resistance of iron wire of particular length and thickness is 1 ohm. If the length and the diameter of wire both are doubled, then the resistivity in ohm m will be :

1. 1 × 10–7

2. 2 × 10–7

3. 4 × 10–7

4. 8 × 10–7

Subtopic:  Derivation of Ohm's Law |
 67%
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PMT - 1983
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