ENERGY, POWER AND RESISTANCE

Question 1

Draw circuit symbol for diode

Answer 1

Check

Question 2

Draw circuit symbol for battery

Answer 2

Check

Question 3

Draw circuit symbol for variable resistor

Answer 3

Check

Question 4

Draw circuit symbol for thermistor

Answer 4

Check

Question 5

Draw circuit symbol for LDR

Answer 5

Check

Question 6

Equation for resistance

Answer 6

R = V/I

Question 7

Equaition for resistivity

Answer 7

R = (pl)/A

Question 8

WHat is the main electricity supply?

Answer 8

230V

Question 9

What is Ohm’s Law?

Answer 9

Current is directly proportional to potential difference

Question 10

Draw I-V diagrams for a wire, lamp and diode.

Answer 10

Check

Question 11

A metal obeys Ohm’s law. What is it known as?

Answer 11

An ohmic conductor

Question 12

What is reflected by the gradient on a IV graph?

Answer 12

Resistance

Question 13

Resistance increases. What happens to current?

Answer 13

Decreases

Question 14

Why is filament lamo not an ohmic conductor?

Answer 14

More current - electrons drift quicker - more collisions with lattice - ions have higher vibrational energy - less electrons can pass through

Question 15

What is forward bias direction?

Answer 15

The direction is which diodes allow current to flow

Question 16

What is reverse bias direction?

Answer 16

The direction the diode does nto allow current

Question 17

How does diodes stop current flowing in the wrong direction?

Answer 17

Has infinite resistance when current flow in incorrect way

Question 18

What are properties of diodes?

Answer 18

robust, versitile, operate at low potentials, long working life

Question 19

Name examples of where diodes (or LEDs) are used.

Answer 19

Traffic lights, on and off indicators on TV

Question 20

What are the fuctions of thermistors and LDRs?

Answer 20

Designed to respond to external conditions.

Question 21

What is the definition of e.m.f?

Answer 21

The amount of energy transferred from one form of energy to electrical energy per coloumb of charge when charge passes through a power supply

Question 22

What is e.m.f equal to?

Answer 22

The amount of pd across the power supply/battery when there is no current

Question 23

How can e.m.f be measured?

Answer 23

High-resistance voltmeter in parallel

Question 24

What is the equation for e.m.f?

Answer 24

E = W / Q

Question 25

What is the definition for potential difference?

Answer 25

The energy transfered per unit charge from electrical energy to another form of energy per coloumb of charge when charge passes through it.

Question 26

What unit if V equal to?

Answer 26

JC^-1

Question 27

Name for factors that effect resistance?

Answer 27

Material, length, cross-sectional area, temperature

Question 28

If the corss-sectional area increases, what happens to the resistance?

Answer 28

Decreases

Question 29

If the length of the wire decreases, what happens to the resistance?

Answer 29

Decreases

Question 30

What unit is used for electricity bills and why?

Answer 30

Kilowatt-hour We use millions of J per day, cost of 1J is miniscule - not suitable

Question 31

When are electricity bills recorded?

Answer 31

Every 3 months

Question 32

What does 1 kWh mean?

Answer 32

Enery transfered by 1kWh device in one hour

Question 33

Convert 1kWh into Joules.

Answer 33

3.6*10^6

Question 34

Is kWh a unit of power?

Answer 34

No, unit of energy