elec equations

Question 1

What is current?

Answer 1

measure of flow of electrons around the circuit
Rate of flow of charge

Question 2

What is potential difference?

Answer 2

force driving the electrons around the circuit

Question 3

What is resistance?

Answer 3

Everything that resists or opposes the flow of electrons

Question 4

How do electrons move throughout a circuit?

Answer 4

positive to negative
bigger to smaller line

Question 5

relationship between voltage and current

Answer 5

V = IR
- Directly proportional, linear through 0 with an IV graph

Question 6

Describe the filament lamp IV graph and explain it

Answer 6

• Starts going straight up, but then plateaus
• This is because the filament becomes hot enough to produce light
• High temperature means high resistance which means higher voltage is required to push the current

Question 7

How do diodes work and what do their IV graphs look like

Answer 7

• Prevent flow of current in one direction by having a really high resistance in that direction
• This causes there to only be a current in one direction on the IV graph

Question 8

How does an LDR work?

Answer 8

• Higher light intensity, lower resistance

Question 9

How does a thermistor work?

Answer 9

• Higher temp, lower resistance

Question 10

What is charge?

Answer 10

• measure of total current that flowed within a certain time

Question 11

What is the equation for charge?

Answer 11

Q = I x t

Question 12

How is voltage measured in series?

Answer 12

• Potential difference of battery is the total of potential difference around each component

Question 13

How is current measured in a series circuit?

Answer 13

• Current is same within part of each circuit

Question 14

How is resistance measured in series?

Answer 14

• Total resistance is sum of resistance around each component

Question 15

How is voltage measured in parallel?

Answer 15

• Parallel circuits have the same voltage in each loop

Question 16

How is current measured in parallel?

Answer 16

• Total of each loop’s current is the total current

Question 17

How does resistance work in parallel?

Answer 17

• Resistance reduces the more components there are
• This is because there are more paths for charge to flow, reducing overall resistance

Question 18

How does a resistor work when current passes through it?

Answer 18

There is an energy transfer which heats the resistor due to collisions between the electrons and the ions in the lattice
- heat is dissipated to the surroundings when electric current does work against electric resistance

Question 19

How do low resistance wires help with energy loss?

Answer 19

• Low resistance means that the current has to do less work against resistance, which therefore means less heat being dissipated to the surroundings

Question 20

Advantages and disadvantages of heating affect in a current

Answer 20

Disadvantages:
- Reduces efficiency
- temperature gets too high, stops components working
- requires fuse
Advantages
- Good to heat shit

Question 21

What is electric power?

Answer 21

• Energy transferred per second

Question 22

equations for energy produced in a circuit

Answer 22

E = I x V x t
power x time

E = Q x V

Question 23

equations for power in a circuit

Answer 23

P = e/t
P = IV
P = I^2 * R

Question 24

What is UK main’s supply?

Answer 24

50hz and 230V

Question 25

What happens in the live wire

Answer 25

• Brown
• Carries the voltage, alternates between a high positive and negative voltage

Question 26

What happens in the earth wire

Answer 26

• Green and yellow
• Safety, protects wiring as it carries currents away if something goes wrong, stopping the casing from going live. 0Volts

Question 27

What happens in the neutral wire?

Answer 27

• Blue
• Completes the circuit, current flows through the neutral and live wires
• 0 volt

Question 28

What is a fuse?

Answer 28

A fuse melts when there is a surge in current, breaking the circuit preventing fires or electric shock.

Question 29

Why are switches and fuses connected to the main current?

Answer 29

so that the circuit can be broken as the live wire carries the p.d.

Question 30

How does a circuit breaker work

Answer 30

• Like a fuse detects a surge, but turns off the circuit breaker mechanism
• Shuts the circuit
• Can be turned on again, so cheaper than fuses

Question 31

What is power rating?

Answer 31

• Greater power rating means greater energy consumption per second
• Uses more energy in a given time