If I be the current limit of a fuse wire of length l and radius r, then select the appropriate relation

(1) $I \alpha l$

(2) $I \alpha r^2$

(3) $I \alpha l^0$

(4) $I \alpha r^0$

A current of 1 mA is flowing through a copper wire. How many electrons will pass a given point in one second  $\left[\mathrm{e} = 1.6 \times {10}^{-19} \mathrm{Coulomb}\right]$

1.  $6.25 \times {10}^{19}$

2.  $6.25 \times {10}^{15}$

3.  $6.25 \times {10}^{31}$

4.  $6.25 \times {10}^8$

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. \(\frac{v}{8}\)

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?

The current I as shown in the circuit will be:

1.  10 A

2.  $\frac{20}{3}$ $\mathrm{A}$ $$

3.  $\frac{2}{3}$ $\mathrm{A}$ $$ $$

4.  $\frac{5}{3}$ $\mathrm{A}$

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 $\Omega$

3. 11.1 $\Omega$

A galvanometer of resistance 240 Ω allows only 4% of the main current after connecting a shunt resistance. What is the value of shunt resistance?

1.  10 $\mathrm{\Omega }$

2.  20 $\mathrm{\Omega }$

3.  8 $\mathrm{\Omega }$

4.  5 $\mathrm{\Omega }$

The current in a wire varies with time according to the relation i= (3+2t) A. The amount of charge passing a cross section of the wire in the time interval t=0 to t=4.0 sec would be: (where t is time in seconds)

If a resistance coil is made by joining in parallel two resistances each of 20$\Omega$. 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

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