Questions 4 - Electrostatic

Questions (with answers)
1. A plastic rod is rubbed with a cloth. When placed near pieces of paper, it will:
a) attract them
b) repel them
c) neither (do nothing)
Answer: a - it will attract them because the rod is charged

2. When rubbed with the same cloth, describe what would happen to a copper rod.
Answer: It would not become charged, because copper is a conductor.

3. When an insulator becomes positively charged it:
a) gains electrons
b) loses electrons
c) gains protons
Answer: b - this is because electrons have a negative charge, so if it has less electrons, it will be positive. It cannot be b, because that would mean the negative charge increases, so it would be negative. It definitely cannot be c because protons cannot move. 

4. You wash and dry your hair, then comb it with a plastic comb.  As you move the comb away from your head some hairs are attracted to the comb.

(a) What has happened to the comb to make it attract the hairs? (1 mark)

Answer: It has been charged by friction because you used it to comb your hair - it is an insulator and so is your hair.

(b) If the comb is now held above some small pieces of dry tissue paper what is likely to happen? (1 mark)

Answer: Comb will attract the paper

(c) If you rub your hands all over the comb it will no longer attract your hair.
Explain why. (2 marks)

Answer: You are standing on the ground, so the electrons from the comb will travel through you down to the Earth so the comb is no longer charged, therefore the electrons and the charge is gone.

Do-them-yourself questions (not answered)

1. One method of painting a car uses electrostatics. A paint spray produces paint droplets, all of which are given a positive charge. The car body is given a negative charge.

(a) Explain why it is important to give all of the paint droplets a positive charge. (2 marks)

(b) Explain why it is important to give the car body a negative charge. (2 marks)

2. An aircraft is being refuelled after a long flight. Explain why it is important that, before refuelling starts, the aircraft is first connected to the fuel pump by a metal wire. (4 marks)

More practice questions

Go to this website for more practice - the answers are provided so you can mark your work. Cheating is pointless..the only person that's going to benefit from doing these questions honestly is you.

Revision top tip - make a list of everything you did wrong and then work on that. Then search for more questions and re-do and mark.

Disclaimer: The questions were not created by me, with the exception of question 2 on the answered questions. All rights and credit goes to the person that wrote them, the author, who I was not able to find. Questions 1 and 3 come from BBC Bitesize and the rest were found on a website with no author. I mean no harm. Seriously.

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