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Question 1

Static electricity:

Answer 1

1. When certain insulating materials are rubbed together, negatively charged electrons are scraped off one material and dumped on the other.
2. This will leave the materials electrically charged, with a positive static charge on one and an equal negative static charge on the other.
3. Which way the electrons are transferred depends on the two materials involved.
4. If enough charge builds up, it can suddenly move, causing sparks or shocks.

Question 2

Similar charges…

Answer 2

…repel.

Question 3

Opposite charges…

Answer 3

…attract.

Question 4

What is an electric field?

Answer 4

An electric field is the space surrounding any electric charge, where its effects can be felt.

Question 5

What type of circuit can current flow round?

Answer 5

Current can only flow round a closed circuit.

Question 6

What is electric current?

Answer 6

Electrical current is the rate of flow of electrical charge.

Question 7

What is potential difference?

Answer 7

Potential difference (or voltage) is the driving force that pushes the charge round. Its unit is volt.

Question 8

What is Resistance?

Answer 8

Resistance is anything that resists the flow of charge. All circuit components have a resistance, but you can usually ignore the resistance from wires connecting components as it’s too small. Unit: Ohm

Question 9

Charge (coloumbs,C)=

Answer 9

current (A) x time (s)

Question 10

Potential difference (V)=

Answer 10

current (A) x resistance

Question 11

What does the term I-V characteristic refer to?

Answer 11

The term “I-V characteristic” refers to a graph which shows how the current (I) flowing through a component changes as the potential difference (V) across it is increased.

Question 12

What is a diode?

Answer 12

A diode is a special device made from semiconductor material such as silicon, it lets current flow freely through it in one direction, but not in the other.

Question 13

What does LDR stand for?

Answer 13

LDR stands for “Light dependent resistor” and it is a resistor that’s dependent on the intensity of light. So at a constant light level, its resistance is constant.

Question 14

What is a thermistor a type of?

Answer 14

A thermistor is a type of temperature dependent resistor.

• In hot conditions the resistance of a thermistor drop.
• In cooler conditions, the resistance goes up.

Question 15

What can sensing circuits be used for?

Answer 15

Sensing circuits can be used to turn on or increase the power to components depending on the conditions that they are in.

Question 16

What is potential difference between 2 points equal to?

Answer 16

Potential difference between two points is equal to the work done per unit charges flowing between those two points.

Question 17

Potential difference=

Answer 17

work done (energy transferred) / charge

Question 18

Energy transferred (work done)=

Answer 18

charge x potential difference

Question 19

What do power ratings on devices tell you?

Answer 19

The power ratings tell you the rate that energy is transferred to them from a power supply. Some of this energy will be transferred to its surroundings though.

Question 20

What is power measured in?

Answer 20

Watts (W)

Question 21

Power(W)=

Answer 21

energy(j) / Time(s)

Question 22

Power(W)=

Answer 22

potential difference(V) x current (A)

Question 23

Power(W)=

Answer 23

current^2 x resistance

Question 24

In a series circuit the different components are…

Answer 24

…end to end, between the +ve and -ve terminals of the power supply.

Question 25

In parallel circuits each branch is…

Answer 25

…separately connected to the +ve and -ve terminals of the supply.
-Parallel circuits are usually the most sensible way to connect things, fro example in cars and in households, where you have to be able to switch everything on and off separately.

Question 26

In a series circuit, the total potential difference (p.d) of the supply is…

Answer 26

…shared betweeen various components. So the p.d across the components in a series circuit always add up to equal the p.d. across the power supply.