Class 8
Chapter 4
Page no 66
Answer the following questions :
1. Which energy transformation occurs during magnetic effect of current?
Ans. Electrical energy transforms into magnetic energy during the magnetic effect of current.
2. Which metal is used for making the core of an electromagnet?
Ans. Soft iron is used for making the core of an electromagnet.
3. Name two devices which are based on the use of electromagnet.
Ans. Electric bell and Speakers.
4. Name two factors on which strength of an electromagnet depends.
Ans. Two factors on which strength of an electromagnet depends are:
i) The number of turns in the coil
ii) The strength of the current flowing through the coil.
Page no 69
Choose the correct option:
1. Which of the following factors affect the heat produced in a resistor ?
a) Amount of current passed
(b) Duration for which current flows
(c) Nature of the material
(d) all of them
Ans. (d) all of them
2. The heating coil in an electric iron is usually made of:
(a) Copper. (b) Aluminium
(c) Silver. (d) Nichrome
Ans.(d) Nichrome
3. What is the main purpose of using an electric fuse in a circuit?
(a) To increase brightness of bulbs
(b) To prevent damage or fire during excessive current flow
(c) To store electrical energy
(d) To control voltage
Ans. (b) To prevent damage or fire during excessive current flow
4. In steel manufacturing industries, electric current is used to :
(a) Cool molten steel
(b) Produce magnetic field
(c) Generate high heat to melt and recycle scrap steel
