Electricity & Using Electricity

Question 1

Power supply

Answer 1

Where the energy that is supplied to the circuit comes from.

Question 2

Switch

Answer 2

A switch is an electrical component that opens or closes the circuit. This causes the current to turn on and off.

Question 3

Light bulb

Answer 3

Emanates light when supplied with power from the circuit. It has a tungsten filament meaning it has a very high melting point. The current flows through the filament with a temp. of 2500 °C so that it emits light.

Question 4

Voltmeter

Answer 4

Measures the voltage or energy of the charge carriers.

Question 5

Ammeter

Answer 5

Measures the amount of electrons that pass through a point in a second. (number of coulombs that pass through each second) called amperes.

Question 6

Resistor

Answer 6

Limits the current that passes through by turning electrical energy into heat.

Question 7

Variable resistor (rheostat)

Answer 7

A resistor which can have its value changed.

Question 8

Fuse/Circuit breaker

Answer 8

Thin piece of copper that melts if the filament gets to hot (if the current gets too high)

Question 9

Multimeter

Answer 9

Can measure both amperes and volts.

Question 10

Explain the difference between voltage and current when in parallel circuits and series circuits.

Answer 10

Voltage - When in a series circuit the number of volts are divided for every light bulb but when in a parallel circuit the number of volts stay the same per bulb.

Current - When in a series, the number of amps stay the same per light bulb but in a parallel circuit the amps are divided for every light bulb.

Question 11

If a cell is supplying 12V to three bulbs in a series circuit how many volts would each bulb have?

Answer 11

4V

Question 12

If a cell is supplying 12V to three bulbs in a parallel circuit how many volts would each bulb have?

Answer 12

12V

Question 13

If a cell is supplying 12A to three bulbs in a series circuit how many volts would each bulb have?

Answer 13

12A

Question 14

If a cell is supplying 12A to three bulbs in a parallel circuit how many volts would each bulb have?

Answer 14

4A

Question 15

What is the main metal used in electric circuits?

Answer 15

Copper

Question 16

What do many heavy industries and power transmission companies use in their circuits and why?

Answer 16

Aluminium as it is less expensive compared to copper.

Question 17

State Ohm’s law

Answer 17

V = IR,

Question 18

What is the unit for Power

Answer 18

The unit is Watt, W (1W = 1J/s)

Question 19

State the formula for power consumption

Answer 19

Power = Voltage x Current, P=VI

Question 20

What is the unit used for power consumption in households

Answer 20

kW/h

Question 21

What are ferro-magnetic substances?

Answer 21

Magnetic materials such as iron, some steels, nickel and cobalt.

Question 22

What are magnetic poles?

Answer 22

They are places on a magnet to which magnetic materials are attracted.

Question 23

What is the law of magnetic poles?

Answer 23

Like poles attract, Unlike poles attract.

Question 24

In which direction do field lines move?

Answer 24

From North to South

Question 25

Explain how an electromagnet works?

Answer 25

They are temporary magnets that can be made by passing an electric current through a coil of wire. The magnetic field can be increased by putting an iron bar in the coil. This is called a solenoid.

Question 26

What is a relay?

Answer 26

A relay is a switch. It switches a smaller current and this causes a larger switch to be turned on.

Question 27

What are the 3 types of diodes?

Answer 27

(1) Power diode or Diode (2) Light Emitting Diode or LED (3) Zener Diode

Question 28

Explain the function of a diode

Answer 28

A simple device that allows the current to move in only one direction. A diode can pass current in circuit once the voltage has equalled exceeded 0.7V. When in reverse bias (diode is facing the opposite way) the current can only pass through at a 1000V as this is when the diode begins to break down.

Question 29

What is an LED

Answer 29

An LED behaves like a normal diode in forward and reverse bias. However, when it is in forward bias the diode gives off light.

Question 30

Explain the zener diode

Answer 30

Zener Diodes can be easily broken down in both forward and reverse bias. When it reaches its zener potential the current will pass through when the diode is in reverse bias. E.g. if a Zener diode is rated 6V8 its zener potential is 6.8V

Question 31

Explain a capacitor

Answer 31

A capacitor acts as an energy store. They act as an energy supply when, for example, the energy supply of computers are suddenly interrupted. This protects equipment from transient electrical spikes

Question 32

Explain transistors

Answer 32

A transistor is a semiconductor device used to amplify and switch electrical signals and electric power.

Question 33

What are the three legs of transistors called?

Answer 33

base, emitter and collector.

Question 34

How do you calculate current gain?

Answer 34

current gain = collector current/base current