# A current of 1 mA is flowing through a copper wire. How many electrons will pass a given point in one second  1.   2.   3.   4.

Subtopic:  Current & Current Density |
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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 |
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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 |
60%
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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 |
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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%
From NCERT
PMT - 1983
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The resistivity of a wire :

 1 Increases with the length of the wire 2 Decreases with the area of cross-section 3 Decreases with the length and increases with the cross-section of the wire 4 None of the above statement is correct
Subtopic:  Derivation of Ohm's Law |
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From NCERT
PMT - 1984
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Drift velocity $$v_d$$ varies with the intensity of electric field as per the relation:
1. $$v_{d} \propto E$$
2. $$v_{d} \propto \frac{1}{E}$$
3. $$v_{d}= \text{constant}$$
4. $$v_{d} \propto E^2$$

Subtopic:  Current & Current Density |
78%
From NCERT
PMT - 1981
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In a conductor 4 coulombs of charge flows for 2 seconds. The value of electric current will be :

(1) 4 volts

(2) 4 amperes

(3) 2 amperes

(4) 2 volts

Subtopic:  Current & Current Density |
90%
From NCERT
PMT - 1984
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The specific resistance of a wire is ρ, its volume is 3 m3 and its resistance is 3 ohms, then its length will be

(1) $\sqrt{\frac{1}{\rho }}$

(2) $\frac{3}{\sqrt{\rho }}$

(3) $\frac{1}{\rho }\sqrt{3}$

(4) $\rho \sqrt{\frac{1}{3}}$

Subtopic:  Derivation of Ohm's Law |
80%
From NCERT
PMT - 1984
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