Heating Effect of Electric Current

Q.

An electric heater of resistance 8 ohms draws 15 A from the service mains for 2 hours. Calculate the rate at which heat is developed in the heater. (Give your answer in $\frac{J}{s}$)

1. 1800

2. 1600

3. 500

4. 800

Q.

Why are the conductors of electric heating devices like toasters and irons composed of an alloy rather than a pure metal?

Q.

The induction furnace is based on the heating effect of

1. Electric field

2. Eddy current

3. Magnetic field

4. Gravitational field

Q.

In a cathode ray tube, the filament is made up of tungsten because

1. It can generate large number of electrons as it has small work function

2. It can generate large number of electrons as it has low melting point

3. It can generate large amount of heat, to heat the cathode, as it has low resistivity and high melting point

4. It can generate large amount of heat, to heat the cathode, as it has high resistivity and high melting point

Q.

Nichrome is used in the coils of a heater because of its ______________.

1. low resistance and low melting point

2. high resistance and low melting point

3. low resistance and high melting point

4. high resistance and high melting point

Q. Why nichrome wire is used for making heatng coils in electrical heaters?

1. Nichrome wire is 100 times less resisistive than copper

2. Nichrome wires do not oxidize quickly.

3. Nichrome wires are 100 times more resisistive than copper

4. Copper is not an affordable metal to be used in the heaters.

Q.

Which of the following appliance does not use heating effect of current?

1. Electric bulb

2. Electric iron

3. Electric fan

4. Geyser

Q.

An electric iron is rated $220\mathrm{V},1KW$. Under normal working conditions, find the resistance of the heating element in the iron.

Q.

What type of energy conversion takes place when an electrical bulb is used for producing light and heat?

Q.

When we switch ‘ON’ an electric bulb, after sometime the bulb would become hot.

1. False

2. True

Q.

Question 12
If the current I through a resistor is increased by $100\%$ (assume that temperature remains unchanged), the increase in power dissipated will be

(a) $100\%$
(b) $200\%$
(c) $300\%$
(d) $400\%$

Q.

Two bulbs A & B rated [200V, 50W] and [200V, 100W] are connected in series. Which will glow brighter?

1. Bulb B

2. Bulb A

3. Same brightness

4. 'A’ glows; ‘B’ does not

Q.

A transformer is often filled with oil. The oil used should have.

1. low viscosity

2. high dielectric strength

3. low boiling point

4. high thermal conducting

Q.

Which of the following do not use heating coil?

1. Electric iron

2. Electric stove

3. Microwave oven

4. Induction cooker

Q.

The heating element of electric appliances is made of ______.

Q.

Why is Tungsten metal not used as a Thermionic emitter? How is it modified to be a good Thermion emitter?

1. i) because it has high work function ii) by coating with a substance with high work-function

2. i) because it has low work function ii) by coating with a substance with low work-function

3. i) because it has high work function ii) by coating with a substance with low work-function

4. i) because it has low work function ii) by coating with a substance with high work-function

5. i) because it has very high work function ii) by coating with a substance with high melting point

Q.

The electrical particle which is responsible for the heating effect in the conductors is ______.

1. proton

2. neutron

3. nucleons

4. electron

Q.

An electric bulb works on which of the following principles:

1. Magnetic effect of electric current

2. Chemical effect of electric current

3. Heating effect of electric current

4. Both A and B

Q. Why electric field line is more fundamental than electric field?

Q.

Which of the following appliance does not use heating effect of current?

1. Electric iron

2. Electric bulb

3. Geyser

4. Electric fan

Q.

Two certain appliances A and B are rated as 10kW, 230V and 100W, 230V. Which of the following statement can be regarded correct according to the given data?

1. appliance A draws less current than B

2. appliance B generates more heat than A

3. appliance A has less resistance than B

4. appliance B has less resistance than A

Q. Give Scientific Reasons :
Tungsten is used to make a solenoid type coil in an electric bulb.

Q.

An electric oven of 2 kW is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What results do you expect? Explain.

Q. An electrical appliance has a rating 100 W, 120 V. The resistance of element of appliance when in use is :

1. $1\cdot 2\Omega$
2. $144\Omega$
3. $120\Omega$
4. $100\Omega$

Q. A battery is rated 12 V. Calculate the amount of energy that has to be spent by the battery to discharge 1.2 x 1040 electrons in a circuit.

Q. Name the material which is used for making the heating element of an electric iron.

Q. A battery is rated 12 V. Calculate the amount of energy that has to be spent by the battery to discharge 1.2 x 1040 electrons in a circuit.

Q.

why is tungsten metal selected for making filaments of incandescent lamp bulbs

Q. Why electric field intensity is called vectorial strength

Q.

Mike got an electric cable containing a single copper wire of radius 9 mm and resistance 5 Ω. But his electrician asked him to get a cable with six similar copper wires connected end to end, each of radius 3 mm. What will the resistance of the cable, prescribed by the electrician?