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?

 

Answer:

 

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