Energy Equations

Question 1

What is the equation for efficiency?

Answer 1

Useful power output/ total power input

Question 2

What is the equation for kinetic energy?

Answer 2

1/2mv squared

Question 3

What is the equation for gravitational potential?

Answer 3

Ep= mgh

Question 4

What is the equation for elastic potential?

Answer 4

Ee= 1/2 ke squared (1/2* spring constant* extension squared)

Question 5

What is the equation for specific heat capacity?

Answer 5

Mass* specific heat capacity* temp change

Question 6

What is the specific latent heat of vaporisation?

Answer 6

The energy needed to change the STATE of a 1kg of substance from liquid to gas or gas to liquid

Question 7

What is the equation for work done?

Answer 7

Force* distance

Question 8

What are the 8 energy stores?

Answer 8

• chemical
• kinetic
• gravitational
• elastic
• thermal
• magnetic
• electrical
• nuclear

Question 9

What are the 5 energy pathways?

Answer 9

-Mechanically
- electrically
- heating
- radiation

Question 10

How do thermal power stations work?

Answer 10

Coal burnt to produce electricity+ small bit of chemical energy converted to useful electrical energy. Waste energy lost into surroundings

Question 11

What is the difference between metal and plastic?

Answer 11

Plastic= insulator
Metal= conductor

Question 12

What is the difference between alternating current and direct current?

Answer 12

Current in direct current only flows in one direction
Alternating current flows in different directions and can change in magnitude

Question 13

What happens to wastes energy?

Answer 13

Converted to thermal+ transferred to the surroundings

Question 14

What is the national grid?

Answer 14

A system of cables and transformers connecting power stations to homes and businesses

Question 15

Electrical appliances are connected using the three core cable, what are the three cables?

Answer 15

• brown (live wire)
• blue (neutral)
• yellow/green ( earth wire)

Question 16

What is the pd of the brown wire?

Answer 16

230V

Question 17

How do we recognise a fault in the appliance by the earth wire?

Answer 17

If it’s not 0V

Question 18

What is the fuses job?

Answer 18

Melts/ stops flows of circuit if there is an excessive current

Question 19

What does a diode do?

Answer 19

allows current to flow one way in a circuit

Question 20

What does a resistor do?

Answer 20

Provides fix resistance

Question 21

What is a variable resistor?

Answer 21

Component whose resistance can be changed

Question 22

What does a thermistor do?

Answer 22

Changes resistance with temperature. (Higher temp= lower resistance)

Question 23

What does an LED do?

Answer 23

allows current to flow only one way

Question 24

What does an LDR do?

Answer 24

Has resistance that changes

Question 25

What is the current like in a series circuit

Answer 25

Same in all points

Question 26

What is the PD like in a series circuit?

Answer 26

Shared between components equally if identical resistance

Question 27

What is the current like in a parallel circuit?

Answer 27

Current shared among branches

Question 28

What is the PD like in a parallel circuit?

Answer 28

Same across all components

Question 29

What is the resistance like in a parallel circuit?

Answer 29

Less than that of the lowest resistor