Physics
An electric iron is rated 220V, 2 kW.
(i) If the iron is used for 2h daily, find the cost of running it for one week if it costs ₹4.25 per kWh.
(ii) Why is the fuse absolutely necessary in a power circuit?
Answer
Given,
power P = 2 kW,
time t = 2h,
number of days = 7 and cost = ₹4.25 per kWh
Electrical energy consumed = Power x total time
= 2 kW x (2 x 7) h
= 28 kWh
Cost = 28 x 4.25 = ₹119
∴ Cost of running the iron for a week is ₹119
(ii) The appliances connected to the power circuit like air conditioner, geyser, washing machine, etc. consume heavy current. The fuse is absolutely necessary in a power circuit because if somehow the circuit is overloaded (i.e., the total power of appliances connected in the circuit exceeds the power limit of the circuit) an excessive current will flow in the circuit and the line wire or appliances may get damaged. Moreover, due to the excessive heat produced by such high current, the wires may get overheated causing a fire. The use of fuse in power circuit will safe guard against any such mishap.
Related Questions
(i) Find the equivalent resistance between A and B.
(ii) State whether the resistivity of a wire changes with the change in the thickness of the wire.
(i) Heat supplied to a solid change it into liquid. What is this change in phase called?
(ii) During the phase change does the average kinetic energy of the molecules of the substance increase?
(iii) What is the energy absorbed during the phase change called?
(i) A fuse is rated 8A. Can it be used with an electrical appliance rated 5 KW, 200 V? Give a reason.
(ii) Name two safety devices which are connected to the live wire of a household electric circuit.
(i) State two differences between "Heat Capacity" and "Specific Heat Capacity".
(ii) Give a mathematical relation between Heat Capacity and Specific Heat Capacity.