Electricity

Question 1

What are conductors?

Answer 1

Conductors are materials that allow the flow of electric charge. Metals are good conductors.

Question 2

What are insulators?

Answer 2

Insulators are materials that do not allow the flow of electric charge. Plastic is an example of a good insulator

Question 3

Why can conductors carry a charge?

Answer 3

The delocalized electrons are free to flow through the metal and so carry a current. Insulating materials do not contain free electrons and so current is unable to flow.

Question 4

Why can insulators not carry a charge?

Answer 4

Insulating materials do not contain free electrons and so current is unable to flow.

Question 5

Why are wires coted in plastic?

Answer 5

To prevent electric shocks, the metal wires are coated with a thick layer of plastic.

Question 6

What is conventional current?

Answer 6

When positively-charged particles moving from the
positive terminal around a circuit to the negative terminal.

Question 7

What is electron flow?

Answer 7

It is now known that charge is carried by electrons, flowing from the negative terminal to the positive terminal.

Question 8

What is an electric circuit?

Answer 8

An electric circuit is a path for electric charge to flow along.

Question 9

What is needed for an electric current to work?

Answer 9

• A source of energy
• A component
• A complete loop
• No short circuits

Question 10

What is a short circuit?

Answer 10

If current can flow along a path without passing through the components this part of the circuit is called a short circuit.

Question 11

All circuit symbols?

Answer 11

• Switch
• Cell
• Battery
• Resistor
• Variable resistor
• Fuse
• Voltmeter
• Ammeter
• lamp

Question 12

Are ammeters always connected in series or parallel?

Answer 12

Series

Question 13

Are voltmeters always connected in series or parallel?

Answer 13

Parallel

Question 14

Which sides of a cell are positive or negative?

Answer 14

The left side is positive an the right side is negative

Question 15

Finding the cell polarity?

Answer 15

Look in book but add up all the voltages

Question 16

What is current and the formula to find it?

Answer 16

Current is the rate of flow of charge and is shown in the formula:

I = Q/t

I = Electrical Current in Amps/A
Q = Electrical Charge in C
t = Time in Seconds/S

Question 17

What is the formula for Ohms law?

Answer 17

V = RI

Question 18

What does the gradient of a V-I graph show?

Answer 18

Resistance

Question 19

What does the gradient of a I-V graph show?

Answer 19

1/Resistance

Question 20

How do you know the gradient on a graph is cosntant?

Answer 20

Straight line
Through the Origin

Question 21

What is an example of an ohmic conductor?

Answer 21

A metal at a constant temperature

Question 22

How is a constant temperature of the ohmic conductor maintained?

Answer 22

By opening and closing the switch to break the circuit

Question 22

What component must be included when finding the voltage and current within a circuit with an ohmic conductor?

Answer 22

A variable resistor to change the voltage and current and get at least ten results

Question 23

What factors need to be kept constant to make the test fair when finding the voltage and current within an ohmic conductor circuit?

Answer 23

Temperature
Thickness
Same Metal

Question 24

What is an ohmic conductor?

Answer 24

An ohmic conductor is one in which the potential difference is directly proportional to the current passing through it. Provided the material is maintained at a constant temperature

Question 24

What is known about the current in the series circuit?

Answer 24

The current is the same everywhere

Question 25

What is known about the voltage in the series circuit?

Answer 25

Total voltage in = total voltage out

Question 26

What is known about current into a juction?

Answer 26

The current in = Total current out

Question 27

How much voltage does each branch of a parallel circuit have?

Answer 27

Each branch of a parallel circuit has the same voltage applied

Question 28

How to find the total resistance in parallel?

Answer 28

1/Rt = 1/R + 1/R + 1/R …. 1/Rt = 3/R Rt = 1/(3/R) = 1 X R/3 Rt = 1/3 ohms

Question 28

How to find the total resistance in series?

Answer 28

Rt = R1 + R2.....

Question 32

What happens to the gradient of a V-I graph for a filament lamp and then a I-V graph?

Answer 32

For a V-I graph it gradually increases For a I-V graph it gradually decreases

Question 33

What is the relationship between length and resistance?

Answer 33

They are directly proportional when the wire is maintained at a constant temperature When length increases - resistance increases

Question 34

What is the relationship between resistance and area?

Answer 34

They are inversely proportional when the metal is maintained at a constant temperature When area increases - resistance decreases

Question 35

What is electrical current?

Answer 35

Electrons flowing through a metal wire

Question 36

What energy is produced when electrons flow through a metal wire and how is it produced?

Answer 36

Thermal as the the flowing electrons collide with atoms causing them to vibrate more vigorously

Question 37

What is the equation for energy?

Answer 37

E = P X T E = Energy in joules/J P = Power in watts/W T = Time in seconds/s

Question 38

What is the equation for Power?

Answer 38

P = I X R P = Power in watts/W I = Current in Amperes/A V = Voltage in Volts/V

Question 39

What is a fuse?

Answer 39

An electrical appliance that is used to protect users from electric shock When a current larger than the rating of the fuse passes through it, the wire of the fuse melts breaking the circuit

Question 40

What is direct current?

Answer 40

A one-way flow of electrons from negative to positive terminals of a power supply

Question 41

What is alternating current?

Answer 41

The oscillation of electrons or back and forward movement.

Question 42

What is used to display a.c waveforms?

Answer 42

Oscilloscopes / CRO Screens

Question 43

On the graph of an a.c waveform what is the x and y axis?

Answer 43

Y axis = voltage X axis = time

Question 44

How does the direction of the current change in a.c and d.c?

Answer 44

D.C = The current only flows in one direction as a straight line and as a gradually increasing or decreasing line for a changing d.c A.C = The current changes direction 50 times every second - 50Hz

Question 45

What is 1 unit of electricity?

Answer 45

1 kilowatt hour - kWh

Question 46

What is the equation for for determining the amount of energy used in homes and the cost of electricity?

Answer 46

E = P X T Kilowatt - hour = Kilowatt X Hour

Question 47

How is the price somebody pays for their electricity bill calculated?

Answer 47

Cost = Number of Units X Unit Price

Question 48

Where is the switch placed in the circuit and why?

Answer 48

On the live side of the circuit the circuit is only live up to the switch when it is open. Breaking the circuit and making the casing not dangerous to touch.

Question 49

How is a one-way switch used?

Answer 49

To switch on or off a light from just one place by connecting two terminals

Question 50

How is a two-way switch used?

Answer 50

Used to control light from two locations in a house e.g or long hallway/corridor Joined by wires so that flipping either can turn the light on or off.

Question 51

Diagram for a two-way switch?

Answer 51

Look in book - 21/3/25

Question 52

Name all the components of a three pin plug:

Answer 52

Live wire Earth wire Neutral wire Fuse Cable grip Outer insulation

Question 53

Explain how a live wire is used in a three pin plug?

Answer 53

The live wire is brown and is connected to the fuse and the live pin on the right hand side. The electric current uses the live wire as its route in.

Question 54

Explain how a neutral wire is used in a three pin plug?

Answer 54

The neutral wire is blue and is the the route the current takes when it exits an appliance It is normally on the left hand side of the plug.

Question 55

Explain how a earth wire is used in a three pin plug?

Answer 55

The earth wire is yellow and green and is connected to the earth pin. Used to prevent electric shocks when the appliance has a metal casing as it takes away any current away if the live wire comes in contact with the casing

Question 56

Explain how the outer insulation and cable grip is used in a three pin plug?

Answer 56

The outer insulation ensure no wires are exposed and Is secured by the cable grip

Question 57

Three pin plug diagram

Answer 57

Look in book 21/3/25