10. An electromagnet functions when
a. you put a bulb into it
b. electricity flows through it
c. two objects rubbed together
d. you use a horseshoe magnet
11. Which of the following is TRUE about electromagnets?
a. They don't need a battery.
b. They are permanent magnets.
c. Increasing the number of coils makes the electromagnet stronger.
d. Increasing the number of coils makes the electromagnet weaker.
12. What are needed to make an electromagnet?
a. nail, battery, piece of wire
b. bulb, battery, piece of wire
C. switch, piece of wire, nail
d. battery, switch, piece of wire
13. How can you make an electromagnet stronger?
a. by using a bigger core
b. by adding switch into it
c. by increasing the length of the wire
d. Nothing can be done to increase its pov
14. Which of the following electromagnets can attract the most number of thumbtacks?
a. one with 10 coils
c. one with 25 coils
b. one with 20 coils
d. one with 30 coils
d. wire
15. What part of the electromagnet receives electricity and acts as a magnet?
a. battery
b. core
c. switch
16. Which of the following materials can be used as core in making an electromagnet?
a. plastic ruler
b. plastic straw C. Screwdriver
d. wood stic
17. In which of the following materials can you make a stronger electromagnet?
a. one with 20 coils, 2 dry cells, wood as core
b. one with 20 coils, a dry cell, 1 big iron nail
c. one with 20 coils, 2 dry cells, plastic core
d. one with 20 coils, 1 dry cell, 1 small iron nail
18. What will happen when electricity stops flowing through a coil of wire?
a. The core will burn.
c. The core will stop attracting m
b. Nothing will happen to the core.
d. The core will continue attract
d. telephone a
19. Which of the following materials uses an electromagnet?
a ball and bat b. pen and paper c. fork and spoon
d. doorbells
20. Electromagnets are used in the following except
a buzzers
b. television
C. books
D. doorbells​