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

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.

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

1. $I<mspace\; width="1em"></mspace>\alpha <mspace\; width="1em"></mspace>l$

2. $I<mspace\; width="1em"></mspace>\alpha <mspace\; width="1em"></mspace>r^2$

3. $I<mspace\; width="1em"></mspace>\alpha <mspace\; width="1em"></mspace>l^0$

4. $I<mspace\; width="1em"></mspace>\alpha <mspace\; width="1em"></mspace>r^0$

The resistance of platinum wire at 0$°\mathrm{C}$ is 22.05 $\mathrm{\Omega }$ and at 100$°\mathrm{C}$ it becomes 22.70 $\mathrm{\Omega }$. When the wire is heated to a temperature of t$°\mathrm{C}$ the resistance of wire becomes 24.91$\mathrm{\Omega }$. The value of t is 

1.  220

2.  440

3.  310

4.  550

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

$\mathrm{In}<mspace\; width="1em"></mspace>\mathrm{the}<mspace\; width="1em"></mspace>\mathrm{circuit}<mspace\; width="1em"></mspace>\mathrm{shown}<mspace\; width="1em"></mspace>\mathrm{in}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>\mathrm{figure}<mspace\; width="1em"></mspace>\mathrm{if}<mspace\; width="1em"></mspace>\mathrm{power}<mspace\; width="1em"></mspace>\mathrm{dissipated}<mspace\; width="1em"></mspace>\mathrm{in}<mspace\; width="1em"></mspace>9\mathrm{\Omega }<mspace\; width="1em"></mspace>\mathrm{resistor}<mspace\; width="1em"></mspace>\mathrm{is}<mspace\; width="1em"></mspace>144\mathrm{W},<mspace\; width="1em"></mspace>\mathrm{then}<mspace\; width="1em"></mspace>\mathrm{potential}<mspace\; width="1em"></mspace>\mathrm{difference}<mspace\; width="1em"></mspace>\mathrm{across}<mspace\; width="1em"></mspace>3.6\mathrm{\Omega }<mspace\; width="1em"></mspace>\mathrm{resistor}<mspace\; width="1em"></mspace>\mathrm{will}<mspace\; width="1em"></mspace>\mathrm{be}$

1.  36V

2.  18V

3.  9V

4.  Zero

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

1.  $6.25<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^{19}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>$

2.  $6.25<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^{15}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>$

3.  $6.25<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^{31}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>$

4.  $6.25<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^8$

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:

The current \(I\) as shown in the circuit will be: