Static Electricity

Question 0

2. Why is Coulomb’s law an example of an inverse square law? [2006][2005]

Answer 0

Force is inversely proportional to distance squared.

Question 1

1. State Coulomb’s law of force between electric charges. [2005] [2003][2007 OL][2010 OL][2011][2013]

Answer 1

Coulomb’s Law states that the force between two point charges is proportional to the product of the charges ​and inversely proportional to the square of the distance between them.

Question 2

5. Define the unit of charge, the coulomb.

Answer 2

Amount of charge that passes when 1 amp flows for one second

Question 3

6. Define electric field strength. [2009][2007] [2005] [2003] [2002]

Answer 3

Electric field strength is defined as force per unit charge

Question 4

7. Give the unit of electric field strength. [2007][2003]

Answer 4

The unit of electric field strength is the newton per coulomb (N C-1).

Question 5

How to detect the presence of an electrical field

Answer 5

Electroscope

Question 6

Effect of static electricity

Answer 6

Lightning
Static discharge
Receiving shock after walking across carpet

Question 7

Hazards of static electricity

Answer 7

Explosions in FLOUR mills
‘’” when FUELLING aircraft
Electrical shock

Question 8

How to reduce build up of electrical charge

Answer 8

Earthing

Ie. using a conductor to connect the object to the earth which allows the charge to flow to earth).

Question 9

14. Explain why the gold leaf on the electroscope diverges when a positively charged rod is brought close to the metal cap. [2005 OL]

Answer 9

Some of the electrons at the bottom of the electroscope are attracted to the top due to the positive charge on the rod and as a result there is an excess of positive charge on the bottom, including on the gold leaf. Because similar charges repel the gold leaf moves away from the main section.

Question 10

15. Why should the frame of an electroscope be earthed? [2011]

Answer 10

If the frame was charged it would affect the degree of deflection of the leaf.

Question 11

Use of electroscope

Answer 11

Detect charge

Question 12

Charge by induction….

Answer 12

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Question 13

17. All the charge resides on the surface of a Van de Graff generator’s dome. Explain why. [2007]

Answer 13

Like charges repel and the charges are a maximum distance apart on the outside surface of dome.

Question 14

18. Give an application of the fact that all charge resides on the outside of a conductor. [2007]

Answer 14

Electrostatic shielding
Faraday cage
to protect persons or equipment

Question 15

19. How does a full-body metal-foil suit protect an operator when working on high voltage power lines? [2011]

Answer 15

All charges will reside on the outside of the conducting suit (because the suit blocks out external electrical fields) so he won’t get shocked.