Combined Physics - 6.2

Question 1

What are the circuit symbols for a switch (open and closed), a cell and a battery?

Answer 1

Question 2

What are the circuit symbols for a diode, resistor, variable resistor and LED?

Answer 2

Question 3

What are the circuit symbols for a lamp, fuse and voltmeter?

Answer 3

Question 4

What are the circuit symbols for an ammeter, thermistor and LDR?

Answer 4

Question 5

For electrical charge to flow through a closed circuit what must be included?

Answer 5

A source of potential difference

Question 6

What is electrical current and what determines the size of the current?

Answer 6

The flow of electrical charge, determined by the rate of flow

Question 7

What is the equation for charge flow?

Answer 7

Question 8

In a single closed loop, what value would the current have at any point?

Answer 8

The same value

Question 9

What affects the current through a given component?

Answer 9

The resistance of the component and the potential difference across it

Question 10

For a given potential difference, what happens to the current when the resistance increases?

Answer 10

The current gets smaller

Question 11

What equation links potential difference, current and voltage?

Answer 11

Question 12

What happens to the resistance of an ohmic conductor (such as a wire) when the current changes?

Answer 12

The resistance of ohmic conductors doesn’t change with current

Question 13

What happens to the resistance of a diode or filament lamp when current changes?

Answer 13

Resistance increases with temperature, such as the current increases the resistance increases

Question 14

Draw and describe an I-V graph for an ohmic resistor (e.g. a resistor at a constant temperature)

Answer 14

Current (at constant temperature) is directly proportional to potential difference

Question 15

Draw and describe an I-V graph for a filament lamp

Answer 15

As the current increases the temperature of the filament lamp increases (so the resistance increases) meaning less current can flow per unit potential difference

Question 16

Draw and describe an I-V graph for a diode

Answer 16

Current will only flow in one direction (there is a very high resistance in the other direction)

Question 17

What happens to the resistance of a thermistor as temperature increases?

Answer 17

As temperature increases a thermistor’s resistance decreases

Question 18

Where are thermistors commonly found?

Answer 18

Car engine temperature sensors / electronic thermostats (as temperature rises the resistance decreases)

Question 19

What happens to the resistance of a LDR as light increases?

Answer 19

As light increases a LDR’s resistance decreases

Question 20

Where are LDRs commonly found?

Answer 20

LDRs are used as automatic night lights / burglar detectors (in bright light the resistance is low)

Question 21

How are LDRs and thermistors used in sensing circuits?

Answer 21

Sensing circuits can be used to turn on / increase the power to components depending on conditions (e.g. as a room gets hotter the resistance of a thermistor decreases taking a smaller share of the potential difference from a power supply allowing a fan to get more potential difference and spin faster)

Question 22

What are the two ways of joining an electrical component?

Answer 22

In series or in parallel

Question 23

In a series circuit, what is the current like through all components?

Answer 23

The same

Question 24

How is the total potential difference distributed between the components in a series circuit?

Answer 24

It is shared

Question 25

How are step-down transformers used within the National Grid?

Answer 25

Step-down transformers bring the 400’000V of the National Grid down to 230V for domestic use