P4 - Circuit Electricity

Question 1

A charged object creates an…

Answer 1

Electric field around it

Question 2

A second charged object in that field experiences…

Answer 2

A force because of the first electric field. This is a NON-CONTACT FORCE

Question 3

The closer the 2 objects in the electric field…

Answer 3

The stronger the force is between them

Question 4

What is a Non-Contact Force?

Answer 4

A force that acts on an object without touching it

Question 5

How to draw an electric field

Answer 5

Circle with plus or minus in for a positive or negative electric field
Arrows coming out of the circle in the direction that a positive charge would flow in the electric field
(If the field is negative, the arrows will be pointing inwards as opposites attract, but if the field is positive then the arrows will be pointing outwards)

Question 6

How is a stronger electric field showed in a diagram?

Answer 6

More arrows

Question 7

What happens when 2 insulating materials are rubbed against each other?

Answer 7

Electrons are transferred from one material to another

Question 8

If 2 objects are oppositely charged, air molecules in the field between them experience…

Answer 8

A force towards the positively charged object and if the field is strong enough, then some electrons will be pulled from the air molecules. These electrons would then hit other air molecules causing them to also lose electrons. This causes a sudden flow of electrons between the 2 charged objects.

Question 9

Draw out the components of a circuit

Answer 9

Positive and negative terminals
Single Cell
Battery
Open Switch
Closed Switch
Variable Resistor
Thermistor
LDR
Diode
LED
Fuse
Ammeter
Voltmeter

Question 10

What does a single cell do?

Answer 10

Provides cell with potential difference

Question 11

What does a battery do?

Answer 11

Provides cell with potential difference

Question 12

What does an Open Switch do?

Answer 12

Creates a break in the circuit, so turns it off

Question 13

What does a Closed Switch do?

Answer 13

Closes gap in circuit, so turns it on

Question 14

What does a Variable Resistor do?

Answer 14

Can change the resistor with a slider

Question 15

What does a thermistor do?

Answer 15

Changes resistance based on temperature
high temp. = low resistance
low temp. = high resistance

Question 16

What does an LDR do?

Answer 16

Changes resistance based on light supply
bright = low resistance
dim = high resistance

Question 17

What does a Diode do?

Answer 17

Allows current to flow in 1 direction only and converts AC current to DC

Question 18

What does an LED do?

Answer 18

Converts electrical energy directly to light energy

Question 19

What does a fuse do?

Answer 19

Breaks the circuit if a fault happens (if too much current is flowing)

Question 20

What does an Ammeter do?

Answer 20

Measures current

Question 21

What does a Voltmeter?

Answer 21

Measures voltage/potential difference

Question 22

What is Current?

Answer 22

A current is a flow of charge

Question 23

What charge does current have and why?

Answer 23

Current is negatively charged because only electrons move

Question 24

The size of current is…

Answer 24

The rate of charge per second

Question 25

What is the equation linking current, charge and time?

Answer 25

Charge = Current x Time
Q = I t
(Coulombs) (Amps) (Seconds)

Question 26

What is charge measured in?

Answer 26

Coulombs

Question 27

What is current measured in?

Answer 27

Amps

Question 28

What is time measured in?

Answer 28

Seconds

Question 29

What is Potential Difference/Voltage?

Answer 29

A measure of the energy transferred between 2 points in a circuit per unit charge

Question 30

What is the equation linking Energy Transferred, Charge and Voltage?

Answer 30

Energy Transferred = Charge x Voltage
E Q V
(Joules) (Coulombs) (Volts)

Question 31

As electrons flow through a circuit, the energy they carry is…

Answer 31

Transferred to other stores of energy

Question 32

Electrons that flow through wires have to..

Answer 32

Push their way through lots of vibrating atoms in the metal, which causes RESISTANCE

Question 33

What is Resistance?

Answer 33

A measure of the opposition to the charge

Question 34

What is the equation linking Resistance, Current and Voltage?

Answer 34

Voltage = Current x Resistance
V I R
Volts Amps Ohms

Question 35

A connecting wire has a…

Answer 35

Low resistance so that electrons can easily pass through them

Question 36

The thin wire filament in a bulb has a high resistance so that…

Answer 36

The electrons use a lot of energy trying to pass through the wire, which is then transferred into other stores of energy such as heat and light

Question 37

What does a Fixed Resistor’s graph of Voltage and Current look like?

Answer 37

x axis = voltage
y axis = current
straight line through 0,0
directly proportional
gradient does not change so neither does resistance
gradient = 1/R

Question 38

What does a Filament Bulb’s graph of Voltage and Current look like?

Answer 38

x axis = voltage
y axis = current
passes through 0,0
starts flat then goes directly proportional to pass through 0,0
once passed through 0,0 continues directly proportional until it plateaus
During directly proportional section the resistance is constant, as the gradient is constant and the graph follows Ohm’s Law
When the graph is plateauing, the gradient gets shallower (1/R) so resistance is increasing and the bulb is getting hot. The graph is no longer following Ohm’s Law

Question 39

What does a Diode’s graph of Voltage and Current look like?

Answer 39

x axis = voltage
y axis = current
when voltage < 0, the line is flat as current can only flow in one direction when using a diode. resistance is going backwards, so the current is very high
when voltage > 0, the line is still curved but has a steep gradient as there is a low resistance in the