A toaster operating at 240 V has a resistance of 120 Ω. The power is ______.

(a)

400 W

(b)

2 W

(c)

480 W

(d)

240 W

Two wires of A and B with circular cross section made up of the same material with equal lengths. Suppose R_A = 3 R_B, then what is the ratio of radius of wire A to that of B?

(a)

3

(b)

\(\sqrt3\)

(c)

\(\frac{1}{\sqrt3}\)

(d)

\(\frac{1}{3}\)

The temperature coefficient of resistance of a wire is 0.00125 per °C. At 20°C, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at ______.

(a)

800 °C

(b)

700 °C

(c)

850 °C

(d)

820 °C

In Joule’s heating law, when R and t are constant, if the H is taken along the y axis and I² along the x axis, the graph is ______.

(a)

straight line

(b)

parabola

(c)

circle

(d)

ellipse

The temperature co-efficient of resistance for alloys is _____________.

(a)

low

(b)

very low

(c)

high

(d)

very high

If the specific resistance of a potentiometer wire is 10^-7 Om and current flowing through it is 0.1 amp, cross-sectional area of wire is 10^-6 m², then potential gradient will be ________________.

(a)

10^-2 v/m

(b)

10^-4 v/m

(c)

10^-6 v/m

(d)

10^-8v/m

Electric Heaters

(1)

ampere

Electric furnace

(2)

joule

Electrical Lamp

(3)

Tungsten

Current

(4)

Nichrome

Energy

(5)

Molybdenum

Why current is a scalar?

Distinguish between drift velocity and mobility.

State macroscopic form of Ohm’s law.

Define current density.

State Kirchhoff ’s voltage rule.

What is Seebeck effect?

What is Peltier effect?

Define current.

Define resistance.

What is thermoelectric effect?

Determine the number of electrons flowing per second through a conductor, when a current of 32 A flows through it.

The resistance of a wire is 20 Ω. What will be new resistance, if it is stretched uniformly 8 times its original length?

Obtain the macroscopic form of Ohm’s law from its microscopic form and discuss its limitation.

Two electric bulbs marked 20 W – 220 V and 100 W – 220 V are connected in series to 440 V supply. Which bulb will get fused?

For the given circuit find the value of I.