Electricity And Circuits

Question 1

State the difference in currents between a series and parallel circuits

Answer 1

Series - stays same

Parallel - total current splits across branches

Question 2

State the difference in potential difference between a series and parallel circuit

Answer 2

Series - total is shared between components

Parallel - stays same

Question 3

State the difference in resistance between a series and parallel circuit

Answer 3

Series - adding resistors increases resistance

Parallel - decreases when you add a 2nd resistor

Question 4

Why does the resistance decrease in a parallel circuit?

Answer 4

Both resistors have the same p.d

Current has another direction to go in if another loop added
Increasing the total current

Decreasing the resistance

Question 5

What does a voltmeter measure?

Answer 5

Potential difference

Question 6

Define potential difference

Answer 6

Electrical pressure that causes the current to flow

Question 7

What is the ‘energy transferred’ equation ?

Answer 7

Change x p.d

Question 8

What is the unit for ‘changed’?

Answer 8

Coulombs

Question 9

What does an ammeter measure?

Answer 9

Current

Question 10

Define electrical current

Answer 10

Rate of flow of charge

Question 11

Define metal current

Answer 11

Flow of electrons

Question 12

What is the equation for ‘change’ ?

Answer 12

Current x time

Question 13

When is there current in a circuit?

Answer 13

When a closed circuit has p.d

Question 14

When is current conserved?

Answer 14

At a junction in the circuit

Question 15

What is the equation for potential difference?

Answer 15

Current x resistance

Question 16

In resistors, how do current vary?

Answer 16

Current is directionally proportional to the p.d

Question 17

The steep the graph..

Answer 17

Lower the resistance

Question 18

In filament lamps, how does the current vary?

Answer 18

Increasing current = increasing temperature

Resistance increased

Question 19

Why does a increase in temperature mean an increase in resistance?

Answer 19

Temperature make ions vibrate

Therefore its harder for electrons to flow through resistor

Question 20

In diodes, how does current vary?

Answer 20

Current will only flow in one direction

Resistance is high in the other direction

Question 21

What does LDR stands for?

Answer 21

Light dependent resistors

Question 22

How does resistance of LDR’s vary with light intensity?

Answer 22

Bright = resistance decreases

Darkness = resistance increased

Question 23

Examples of LDR’s

Answer 23

Automatic night lights

Burglar detectors

Question 24

How does resistance of thermistors vary with change in temperature?

Answer 24

Hot = resistance decreases

Cool = resistance increased

Question 25

What are thermistors?

Answer 25

Temperature dependant resistors

Question 26

Thermistors in a circuit:

Answer 26

Keep resistance of variable resistor constant

Gradually heat the thermistor

Question 27

LDR’s in a circuit:

Answer 27

Conduct experiment in dim room

Use lamp w/ dimmer switch

Question 28

Diode in a circuit:

Answer 28

Swap the direction

Question 29

What does a IV graph show?

Answer 29

How current varies as you change the p.d

Question 30

What heats a resistor?

Answer 30

Heat energy transfer

Question 31

What is in a resistor?

Answer 31

Electrical current

Question 32

What happens when an electrical current does work against electrical resistance? (Current against resistance)

Answer 32

Electrical energy dissipates as thermal energy

Into the surroundings

Question 33

What is the energy transfer that heats a resistor a result of?

Answer 33

Collisions between electrons and ions in a lattice

Question 34

Disadvantages of heating an electric current

Answer 34

Reduces efficiency- less energy transferred to useful stores

Circuit can melt

Question 35

Advantages of heating a circuit

Answer 35

Good for heating things
E.g toasters

• coil wire w/ high resistance, current passes through increasing temp, cooking the bread