What is the average drift speed of conduction electrons in a copper wire of cross-sectional area $1.0\times {10}^{-7}<mspace\; width="1em"></mspace>{\mathrm{m}}^2$ carrying a current of 1.5 A? Assume that each copper atom contributes roughly one conduction electron. The density of copper is $9.0\times {10}^3<mspace\; width="1em"></mspace>\mathrm{kg}/{\mathrm{m}}^3,$ and its atomic mass is 63.5 u. 

$1.<mspace\; width="1em"></mspace>1.1<mspace\; width="1em"></mspace>\mathrm{mm}<mspace\; width="1em"></mspace>{\mathrm{s}}^{-1}$
$2.<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>2.1<mspace\; width="1em"></mspace>\mathrm{mm}<mspace\; width="1em"></mspace>{\mathrm{s}}^{-1}$
$3.<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>3.1<mspace\; width="1em"></mspace>\mathrm{mm}<mspace\; width="1em"></mspace>{\mathrm{s}}^{-1}$
$4.<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>4.1<mspace\; width="1em"></mspace>\mathrm{mm}<mspace\; width="1em"></mspace>{\mathrm{s}}^{-1}$

Which one of the following is correct?

An electric toaster uses nichrome for its heating element. When a negligibly small current passes through it, its resistance at room temperature (27.0 °C) is found to be 75.3 Ω. When the toaster is connected to a 230 V supply, the current settles, after a few seconds, to a steady value of 2.68 A. What is the steady temperature of the nichrome element? The temperature coefficient of resistance of nichrome averaged over the temperature range involved is 1.70 × 10^–4 °C^–1

^{$1.<mspace\; width="1em"></mspace>{827}^0<mspace\; width="1em"></mspace>C$
$2.<mspace\; width="1em"></mspace>{820}^0<mspace\; width="1em"></mspace>C$
$3.<mspace\; width="1em"></mspace>{847}^0<mspace\; width="1em"></mspace>C$
$4.<mspace\; width="1em"></mspace>{800}^0<mspace\; width="1em"></mspace>C$}

The resistance of the platinum wire of a platinum resistance thermometer at the ice point is 5 Ω and at the steam point is 5.23 Ω. When the thermometer is inserted into a hot bath, the resistance of the platinum wire is 5.795 Ω. The temperature of the bath is:

$1.<mspace\; width="1em"></mspace>300.{20}^{0}C$
$2.<mspace\; width="1em"></mspace>345.{65}^{0}C$
$3.<mspace\; width="1em"></mspace>320.{20}^{0}C$
$4.<mspace\; width="1em"></mspace>400.{12}^{0}C$

A network of resistors is connected to a 16 V battery with an internal resistance of $1\Omega$, as shown in the figure. The equivalent resistance of the network is:

$1.<mspace\; width="1em"></mspace>4\Omega$
$2.<mspace\; width="1em"></mspace>5\Omega$
$3.<mspace\; width="1em"></mspace>7\Omega$
$4.<mspace\; width="1em"></mspace>2\Omega$

A network of resistors is connected to a 16 V battery with an internal resistance of $1<mspace\; width="1em"></mspace>\Omega$, as shown in the figure. The current in $1<mspace\; width="1em"></mspace>\Omega$ resistor between B and C will be:

$1.<mspace\; width="1em"></mspace>4<mspace\; width="1em"></mspace>A$
$2.<mspace\; width="1em"></mspace>2<mspace\; width="1em"></mspace>A$
$3.<mspace\; width="1em"></mspace>1<mspace\; width="1em"></mspace>A$
$4.<mspace\; width="1em"></mspace>3<mspace\; width="1em"></mspace>A$

A network of resistors is connected to a 16 V battery with an internal resistance of $1<mspace\; width="1em"></mspace>\Omega$, as shown in the figure. The voltage drop across AB is:

1. 2 V

2. 25 V

3. 4 V

4. 6 V

A battery of 10 V and negligible internal resistance is connected across the diagonally opposite corners of a cubical network consisting of 12 resistors each of resistance $1<mspace\; width="1em"></mspace>\Omega$ (as shown in the figure). The total current in the network is:

$1.<mspace\; width="1em"></mspace>6<mspace\; width="1em"></mspace>A$
$2.<mspace\; width="1em"></mspace>12<mspace\; width="1em"></mspace>A$
$3.<mspace\; width="1em"></mspace>4<mspace\; width="1em"></mspace>A$
$4.<mspace\; width="1em"></mspace>2<mspace\; width="1em"></mspace>A$

The current in the branch AB in the given network is:

 
1. 5/8 A

2. 5/2 A

3. 15/8 A

4. 3/2 A

The four arms of a Wheatstone bridge have the following resistances as shown in the figure. A galvanometer of 15Ω resistance is connected across BD. What is the current through the galvanometer when a potential difference of 10 V is maintained across AC?

1. 4.87 mA

2. 3.72 mA

3. 5.01 mA

4. 2.65 mA