P3.2

Question 1

What is the link between potential difference, energy and charge?

Answer 1

Potential difference (V)
Energy transferred (J) = ———————————
Charge (C)

Question 2

What is potential difference measured in?

Answer 2

Volts

Question 3

How do you measure current in a series circuit?

Answer 3

With an ammeter

Question 4

How do you measure potential difference in series circuits?

Answer 4

With a voltmeter

Question 5

What happens when two voltmeters are in series?

Answer 5

They add up to give the total potential difference

Question 6

What happens when 2 voltmeters are parallel?

Answer 6

They are both equal to the total potential difference

Question 7

What is the formula for potential difference?

Answer 7

Potential difference = resistant x current

Question 8

Why do some components have resistance?

Answer 8

They have ions in a fixed lattice and when the flow of electrons from the wire collides with the ions, resistance and what is formed

Question 9

What is a variable resistor?

Answer 9

A circuit component that you can use to change the amount of wire or other resisting material

Question 10

Why is a graph of resistance to potential difference linear?

Answer 10

As you increase potential difference, it’s resistance does not change

Question 11

What do you use in a circuit if you need the resistance to be constant?

Answer 11

A resistance wire or a resistor

Question 12

What is Ohm’s law?

Answer 12

The current is proportional to the potential difference if the temperature does not change

Question 13

What is a diode?

Answer 13

A component that only allows a current to flow one way

Question 14

What does LED stand for?

Answer 14

Light-Emitting Diode

Question 15

How do connect an LED to a battery?

Answer 15

The long led of an LED should be connected to the positive terminal

Question 16

What happens to the current and potential difference in a diode?

Answer 16

As you apply potential difference in the forward direction, very little current flows then it suddenly increases.

Question 17

What happens when you reverse the potential difference in a diode?

Answer 17

There is no current

Question 18

When would you use a diode?

Answer 18

When you want the current to flow in only 1 direction

Question 19

What is a thermistor?

Answer 19

An object in which its resistance depends on temperature

Question 20

What is a thermistor made of?

Answer 20

A semiconducting material such as silicon

Question 21

What does a line of constant gradient in a current by PD graph mean?

Answer 21

The component is linea

Question 22

What is the gradient of a current by PD graph?

Answer 22

Opposite of resistance

Question 23

What does a steep gradient mean in a current by PD graph?

Answer 23

Small resistance

Question 24

What does a small gradient mean in a current by PD graph?

Answer 24

Large resistance

Question 25

What does a line of changing gradient mean in a current by PD graph?

Answer 25

The component is non-linear element

Question 26

What is the resistance of a diode in the reverse direction?

Answer 26

Extremely high (infinitely high)

Question 27

How does the resistance of a thermistor change with temperature?

Answer 27

As you increase temperature, resistance decreases

Question 28

Why does an increase of temperature mean a decrease of resistance in thermistors?

Answer 28

As you heat it, more electrons gain enough energy to escape from the atoms in the semiconductor meaning more electrons become available for conduction

Question 29

What does a thermistor look like in a circuit diagram?

Answer 29

A rectangle with a line thorough it which bends outside the rectangle

Question 30

What does an LDR look like in a circuit diagram?

Answer 30

A rectangle surrounded by a circle with 2 arrows pointing at it

Question 31

What does LDR stand for?

Answer 31

Light-dependent resistor

Question 32

How does a light-dependent resistor work?

Answer 32

Its resistance changes with light intensity - as you increase light intensity, resistance decreases

Question 33

Why does an increase of light intensity cause less resistance in an LDR?

Answer 33

Light causes more electrons to be released into the circuit, increasing the current

Question 34

How are current and resistance related?

Answer 34

As you increase current, resistance decreases

Question 35

What does a resistance graph for a thermistor and LDR look like?

Answer 35

Starts high with a curved decrease

Question 36

What would happen if you add another lamp in series?

Answer 36

Current decreases Net resistance increases

Question 37

What happens if you add another lamp in parallel?

Answer 37

Total current increases Net resistance decreases

Question 38

How do you work out net resistance?

Answer 38

Potential difference (V) ——————————— Total current (A) - current at end of circuit

Question 39

What is a milliamp?

Answer 39

1/1000 A

Question 40

How do you calculate potential difference in a sensing circuit?

Answer 40

1. Calculate net resistance (NR) 2. Calculate the current (PD of battery over NR) 3. Calculate PD of what you are looking for (I x R)

Question 41

What is a kilo ohm?

Answer 41

1000 ohms

Question 42

What is power?

Answer 42

The energy transferred per second

Question 43

How is energy transferred related to potential difference?

Answer 43

Potential difference = energy transferred / charge

Question 44

What is the formula for current (in terms of charge)?

Answer 44

Charge ———— Time

Question 45

What are the equations for power?

Answer 45

Potential difference x current Current^2 x resistance

Question 46

What is the formula for energy transferred in Joules per Kilowatt Hour (for home appliances)?

Answer 46

Power (W) x Time (s)

Question 47

What are the units for power?

Answer 47

Warrs