An electric iron rated 750 W is operated for 2 hours/day. How much energy is consumed by the electric iron for 30 days?
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
Which particles are responsible for current in conductors?
Define watt-hour. How many joules are equal to 1 watt-hour?
Name the S.I unit of electrical energy. How is it related to Wh?
An electrical appliance having a resistance of 200Ω is operated at 200 V. Calculate the energy consumed by the appliance in 5 minutes (i) in joules (ii) in kWh.
Two bulbs are rated 60 W, 220 V and 60 W, 110 V respectively. Calculate the ratio of their
resistances
An electric kettle is rated 2.5 kW, 250 V. Find the cost of running the kettle for two hours at Rs. 5.40 per unit.
The diagram above shows a circuit with the key k open. Calculate :
(i) the resistance of the circuit when the key k is open.
(ii) the current drawn from the cell when the key k is open.
(iii) the resistance of the circuit when the key k is closed.
(iv) the current drawn from the cell when the key k is closed.
Express watt hour and kilowatt hour in joule.
State the position of heating element with respect to principal focus of concave reflector and give reason for choosing this position.
An electric filament lamp is connected to a supply of voltage higher than the recommended value. Give reasons, why compared with a normal performance, the lamp emits a brighter light and its life is shortened.
Two lamps are rated 220V, 50W and the other rated 220V, 100W are connected in series with the mains of 220 V. Explain, why the 50W lamp glows more?
Why is the electric power from the generating station transmitted at high voltage?
How does the heat produced by die passage of current in a metallic wire depend on the current in the wire?
How does earthing prevent electrical shock?
You are required to connect a bulb, a fan and a socket outlet to the mains in one set A and an air-conditioner and a refrigerator to the mains in other set B. Will you recommend the wire of same thickness and same insulation in both? explain your answer.
Three 250 W heaters are connected in parallel to a 100 V supply, Calculate total current taken from the supply.
An Electric bulb is marked 100 W, 230 V. What how long would this lamp take to consume one unit of electricity?
Two resistances R1 = 4Ω and R2 = 6Ω are connected in series. The combination is connected with a battery of e.m.f. 6V and negligible resistance. Calculate:
(i) the heat produced per minute in each resistor,
(ii) the power supplied by the battery.
Unit of electric power may also be expressed as:
