Section 2

Question 1

What happens when an electrical charge goes through a change in voltage?

Answer 1

Energy is transferred.

Question 2

Where is energy supplied to the charge?

Answer 2

At the power source.

Question 3

When does charge give up this energy?

Answer 3

When it falls through any voltage drop in components elsewhere in the cv=ircuit.

Question 4

The bigger the change in voltage…

Answer 4

…the more energy is transferred for a given amount of charge passing through the circuit.

Question 5

What is voltage?

Answer 5

The energy transferred per unit charge passed.

Question 6

One volt is?

Answer 6

One joule per coulomb.

Question 7

What happens when two insulating objects are rubbed together?

Answer 7

They’ll leave a positive charge on and a negative charge on the other.

Question 8

When you rub a polythene rod with a duster what becomes positively charged and what becomes negatively charged?

Answer 8

The polythene rod becomes negatively charged and the duster becomes positively charged.

Question 9

When you rub a acetate rod with a duster what becomes positively charged and what becomes negatively charged?

Answer 9

The acetate rod becomes positively charged and the duster becomes negatively charged.

Question 10

How can a charged conductor be discharged safely?

Answer 10

Connecting it to earth with a metal strap. The electrons flow down the strap to the ground if the charge is negative and flow up the strap is the charge is positive.

Question 11

What is electric current?

Answer 11

The rate of flow of electrical charge.

Question 12

The greater the charge on an isolated object…

Answer 12

…the greater the voltage between it and the Earth.

Question 13

How can a spark be caused?

Answer 13

If the voltage gets big enough, a spark will jump across the gap.

Question 14

Same charges?

Answer 14

Repel.

Question 15

Opposite charges?

Answer 15

Attract.

Question 16

How can you see whether a material is charged?

Answer 16

Using a golf leaf electroscope.

Question 17

Describe the gold leaf electroscope.

Answer 17

It has a metal disc connected to a metal rod, at the bottom of which are attached two thin pieces of gold leaf.

Question 18

How does a gold leaf electroscope work?

Answer 18

When a rod with a known charge is brought near to the disc of the electroscope, electrons will either be attracted to, or repelled from the metal disc depending on the charge of the rod.

Question 19

What does the charge do to the electroscope?

Answer 19

This induces a charge in the metal disc, which in turn induces a charge in the gold leaf. Both gold leaves will have the same charge so they repel, causing them to rise.

Question 20

What happens when the rod is moved away from the electroscope?

Answer 20

The gold leaves will discharge and fall again.

Question 21

What is another way of testing whether a rod of material is charged?

Answer 21

Suspend a rod with a known charge on a thread and see if there is repulsion or attraction when the rod you’re testing is brought close to it.

Question 22

How can you demonstrate electrostatic charges?

Answer 22

Using a Van de Graaff generator.

Question 23

What is a Van de Graaff made up of?

Answer 23

A rubber belt moving round plastic rollers underneath a metal dome.

Question 24

How is an electrostatic charge build up on the Van de Graaff?

Answer 24

As the belt goes around charge is build up on the metal dome.

Question 25

How do inkjet printers work?

Answer 25

1. Tiny droplets of ink are forced out of a fine nozzle, making them electrically charged.
2. The droplets are deflected as they pass between two metal plates. A voltage is applied to the plates - one is negative and one is positive.
3. The droplets are attracted to the plate of the opposite charge and repelled form the plate with the same charge.
4. The size and direction of the voltage across each plate changes so each droplet is deflected to hit a different place on the paper.
5. Lots of tiny dos make the printout.

Question 26

How does a photocopier work?

Answer 26

1. The image plate is positively charged. An image of what you’re copying is projected onto it.
2. Whiter bits of what you’re copying make light fall on the plate and the charge leaks away in those places.
3. The charged bits attract negatively charged black powder which is transferred onto positively charged paper.
4. The paper is heated so the powder sticks.

Question 27

What happens when synthetic clothes are dragged over each other or over your head?

Answer 27

Electrons get scrapped off, leaving static charges on both parts, and that leads to the inevitable attraction and little shocks as the charges rearrange themselves.

Question 28

How is lightening caused?

Answer 28

Raindrops and ice bump together inside storm clouds, knocking off electrons and leaving the top of the cloud positively charged and the bottom of the cloud negative. This creates a huge voltage and a big spark.

Question 29

Why can fuel-filling be dangerous?

Answer 29

As fuel flows out of a filler pipe, static can build up which can easily lead to a spark.

Question 30

How are sparks avoided during fuel-filling.

Answer 30

Nozzles are made of metal so that the charge is conducted away, instead of building up. It is also goof to have earthing straps between the fuel tank and the fuel pipe.