Which use more energy, a 250 W TV set in 1 hr, or 1200 W toaster in 10 minutes?

Find the energy in KWh consumed in 10 hours by four devices of power 500W each.

An electric heater is rated 1500 W. How much energy does it use in 10 hours?

Several electric bulbs designed to be used on a 220V electric supply line, are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220V line if the maximum allowable current is 5A?

A person trying to lose weight (dieter) lifts a 10 kg mass, one , thousand times, to a height of 0.5 m each time. Assume that the potential energy lost each time she lowers the mass is dissipated, (a) How much work does she do against the gravitational force? (b) Fat supplies 3.8 xx 10^7 J of energy per kilogram which is converted to mechanical energy with a 20% efficiency rate. How much fat will the dieter use up?

An electron and a proton are detected in a cosmic ray experiment, the first with kinetic energy 10 keV, and the second with 100 keV. Which is faster, the electron or the proton? QBtain the ratio of their speeds, (electron mass = 9.11 xx10^31 kg, proton mass = 1.67 x 10-^27 kg, 1 eV = 1.60 x 10-^9 J)

A family uses 8 kW of power, (a) Direct solar energy is incident on the horizontal surface at an average rate of 200 W per square meter. If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply 8 kW? (b) Compare this area to that of the roof of a typical house.

In a series LCR circuit in which R= 3Omega , L=25mH and C=800muF a sinusoidal a.c. voltage of peak value 250 V is applied. Find current in the circuit at resonant condition.

A battery of e.m.f 2V and internal resistance 1Omega is used to send a current through a potentiometer wire of length 200cm and resistance 4Omega . What length of the wire will be required to balance a cell of e.m.f 1.08V?