AC and DC

Question 1

Current definition

Answer 1

Rate of flow of charge

Question 2

What is current measured in

Answer 2

Amps

Question 3

Charge measured in

Answer 3

Coulombs

Question 4

What can result in a high current

Answer 4

Lots of electrons moving slowly

Question 5

What is direct current

Answer 5

If the current only flows in one direction

Question 6

What can supply DC electricity

Answer 6

Batteries and cells

Question 7

What can current do and not do

Answer 7

Decrease or increase but not change direction

Question 8

What is alternating current

Answer 8

If the current constantly changes direction and goes negative

Question 9

What can supply AC electricity

Answer 9

Mains electricity

Question 10

What is energy transferred at in a circuit

Answer 10

The speed of light

Question 11

What is voltage

Answer 11

Energy per unit charge

Question 12

What is potential difference

Answer 12

Refers to the energy converted from electrical energy per unit charge

Question 13

How can we measure current in series

Answer 13

Using ammeter

Question 14

How can we measure voltage in series

Answer 14

Voltmeter

Question 15

What does a series circuit contain

Answer 15

All components in a single loop

Question 16

What is a parallel circuit

Answer 16

A circuit containing more that one loop or branch, and may have junctions

Question 17

In a series circuit the current is…

Answer 17

The same everywhere

Question 18

In a parallel circuit, the current…

Answer 18

Splits at a junction. The current next to the cell is highest

Question 19

Why is the current next to the cell in a parallel circuit the highest

Answer 19

All electrons must flow from that wire to the rest of the circuit

Question 20

How can the current in a circuit be increased

Answer 20

• Increasing voltage supplied
• Decreasing resistance of a circuit
• Connecting the circuit in parallel (this decreases the resistance)

Question 21

In a parallel circuit the voltage…

Answer 21

Is the same for each branch. The voltage across each branch is equal to the voltage across the battery

Question 22

In series the voltage…

Answer 22

Along a branch, is shared between the components.

Question 23

What determines the voltage across a component

Answer 23

The resistance of the components

Question 24

What causes resistance

Answer 24

Electrons colliding with positive ions that form the structure of the metal wire

Question 25

What happens to energy in a resistor

Answer 25

Chemical energy is transferred into thermal

Question 26

What is resistance measured in

Answer 26

Ohms

Question 27

What does a variable resistor do

Answer 27

Change the resistance in a circuit

Question 28

How does a variable resistor change resistance

Answer 28

Increasing or decreasing the length of wire the electricity has to flow through

Question 29

How does a longer length reduce current

Answer 29

The longer the length, the more electrons collide with ions

Question 30

What does ohms law state

Answer 30

Current through a resistor at a constant temperature is directly proportional to the voltage across for a constant resistance
Voltage = Current X Resistance

Question 31

What is an LDR

Answer 31

Light dependent resistor

Question 32

What does an LDR do

Answer 32

Change resistance with light intensity

Question 33

What do fixed resistors have

Answer 33

A constant resistance

Question 34

What happens with filament bulbs

Answer 34

They do not obey ohm’s law

Question 35

What happens with resistance for an LDR

Answer 35

The higher the light intensity the lower the resistance

Question 36

Where can LDRs be found

Answer 36

Street lamps

Question 37

What does a thermistor do

Answer 37

Change resistance with temperature

Question 38

What happens with resistance in thermistors

Answer 38

The higher the temperature the lower the resistance

Question 39

Where can thermistors be found

Answer 39

Kettles