physics topic two

Question 1

what is the function of a Switch (open)

Answer 1

Electricity can’t flow

Question 2

what is the function of a Switch (closed)

Answer 2

Completes the circuit (lets electricity flow)

Question 3

what is the function of a Cell

Answer 3

Provides PD and current for a circuit

Question 4

what is the function of a battery

Answer 4

Provides PD and current for a circuit

Question 5

what is the function of a lamp/bulb

Answer 5

Converts electrical energy to light energy

Question 6

what is the function of a resistor

Answer 6

Slows down current and voltage

Question 7

what is the function of a voltmeter

Answer 7

Measures PD – volts

Question 8

what is the function of an Ammeter

Answer 8

Measure current – amps

Question 9

what is the function of a fuse

Answer 9

Melts if current gets too high to stop electricity

Question 10

what is the function of a diode

Answer 10

Forces current to only flow in one direction

Question 11

what is the function of a Light Emitting Diode (LED)

Answer 11

Same as diode but gives off light

Question 12

what is the function of a Variable Resistor

Answer 12

Can be used to change the resistance

Question 13

what is the function of a Thermistor

Answer 13

The higher the temperature, the lower the resistance

Question 14

what is the function of a Light Dependant Resistor (LDR)

Answer 14

The higher the light intensity, the lower the resistance

Question 15

what is charge

Answer 15

Charge is the amount of electricity travelling through a circuit.

Question 16

what is current and what is it measured in

Answer 16

a flow of charged particals - measured in amps

Question 17

what is voltage and what is it measured in

Answer 17

a measure of the difference in energy between one part of a circuit and another (How fast electrons move) - measured in volts

Question 18

what is resistance and what is it measured in

Answer 18

the opposition to the flow of electric current in a material or circuit (Slows down current and voltage) - measured in ohms

Question 19

what is potential difference

Answer 19

and what is it measured in

Question 20

what does the resistance in a circuit depend on

Answer 20

The resistance in a circuit will depend on the components used in the circuit as
well as the length of wire used in the circuit. The longer the wire, the greater the
resistance.

Question 21

what a a Circuit in series

Answer 21

Series circuits consist of one loop of wire.

Question 22

give features For components connected in series

Answer 22

there is the same current through each component

the total potential difference of the power supply is shared between the components

the total resistance of two components is the sum of the resistance of each component.

Question 23

what are Parallel Circuits

Answer 23

Parallel Circuits consist of two or
more loops (branches) of wire.

Question 24

give features For components connected in parallel

Answer 24

the potential difference across
each component is the same

the total current through the
whole circuit is the sum of the
currents through the separate
components on each loop
(branch)

the total resistance of two
resistors is less than the
resistance of the smallest
individual resistor.

Question 25

describe the IV Characteristics REQUIRED PRACTICAL

Answer 25

1) Measure the current in resistor using ammeter 2) Measure the p.d. across resistor using voltmeter 3) Vary the resistance of the variable resistor 4) Record a range of values of current and p.d. 5) Reverse connection of resistor to power supply 6) Repeat measurements of I and V in negative direction 7) Plot a graph of current against p.d.

Question 25

what is ohms law

Answer 25

The resistor follows Ohm’s law (it’s an Ohmic conductor) and its resistance is constant.

Question 26

Explain, in terms of the electrons and ions inside the filament, why both the temperature and the resistance increase

Answer 26

Ions in lamp/resistor vibrate faster Electrons collide more with the ions Increasing resistance and decreasing current

Question 27

what is something if its non-Ohmic.

Answer 27

it doesnt follow ohms law

Question 28

what happens to to the resistance of LDR with increasing light intensity

Answer 28

resistance decreases

Question 29

describe Circuit resistance REQUIRED PRACTICAL

Answer 29

1) Have 3 lengths of wire (10cm, 20cm, 40cm) measured with a ruler 2) Measure current and potential difference using an ammeter and voltmeter 3) Take repeat readings and calculate a mean 4) Switch off circuit in between each reading to allow wire to cool 5) Calculate resistance by using: r = v / i 6) Plot a graph of resistance against length

Question 30

what is direct current

Answer 30

Direct current moves in one direction only

Question 31

what is alternating current

Answer 31

Alternating Current repeatedly reverses direction

Question 32

what is The UK mains supply

Answer 32

The UK mains supply is 230 V. and has a frequency of 50 Hz (50 hertz)

Question 33

what are the components of a plug

Answer 33

Live wire (brown) – Carries current and voltage (230V) Neutral wire (blue) – Completes the circuit (0V) Earth wire (green + yellow stripes) – Earths appliance Fuse – Wire inside melts if current gets too high

Question 34

what is the purpose of earthing appliances

Answer 34

if live wire touches case current flows to earth

Question 35

how are plugs double insulated

Answer 35

case is made of insulator (plastic) cable is (also) insulated

Question 36

what is the National grid

Answer 36

A series of transformers, power cables and pylons

Question 37

what are step-up transformers

Answer 37

Increases potential difference Decreases current Reducing thermal energy transfer to surroundings from transmission cables Increasing efficiency

Question 38

what are step-down transformers

Answer 38

Decreases potential difference To a safe value

Question 39

what are static charges

Answer 39

These are positive (+) and negative (-) charges. When two electrical charges interact, they produce Electrostatic forces - non contact forces

Question 40

how does Charging by friction work

Answer 40

When two objects are rubbed together (friction), electrons transfer from one to the other. One object will become positive and the other will become negative

Question 41

what is An electric field the region

Answer 41

the region (around a charged object) where another charged object experiences a force