# Electricity Worksheet-19

Electricity Worksheet-19

1. An electric bulb draws 1.2 A current at 6.0 V. Find the resistance of the bulb.

1. Which will have a higher resistivity: a conductor or an insulator ?

1. Two wires of same material and same length have radii r1 and r2 respectively. Compare their resistances.

1. Name a substance whose resistance decreases with temperature.

1. Name a substance whose resistance almost remains unchanged by increase of temperature.

1. Distinguish between kilowatt and kilowatt hour.

1. Name two special characteristics of a heater coil.

1. A 60 W bulb carries a current 0.5 A. Find the charge that passes through it in 2 hour.

1. Calculate the current through a lamp of 25 W operating at 200 V.

1. Under what conditions is Ohm's law applicable?

1. 1. An insulator

1. If R1 and R2 are resistances of the two wires, 1. Germanium which is a semiconductor.

1. Manganin which is an alloy of Cu, Ni and Mn.

1. A kilowatt (kW) is a unit of power and a kilowatt hour (kWh) is a unit of electric energy.

1kWh = 1 kW × 1h.

1. A heater coil should have (i) high resistivity and (li) high melting point.

1. Q = It = 0.5 × (2 × 60 × 60)

= 3600 C.

1. 1. If the physical conditions like temperature, etc., of a conductor do not change when current is passed through it.