P2

Question 1

What is a series circuit?

Answer 1

Series circuit has no branches and the current can only flow in one path

Question 2

What is current?

Answer 2

An electric current is a flow of electric charge around a circuit
Unit amp(a)

Question 3

How do you measure Current?

Answer 3

You can measure current in a circuit by using an ammeter

Question 4

What is a parallel circuit?

Answer 4

A parallel circuit contains branches and splits currents between branches

Question 5

What is the current like in the parallel circuits?

Answer 5

The current in the branches adds up to the total current leaving the cell

Question 6

What is potential difference?

Answer 6

measure of energy, per unit of charge, transferred between two points in a circuit

Question 7

What we used to measure potential difference

Answer 7

Volt meter

Question 8

What is the potential difference in parallel circuits like?

Answer 8

For components connected in parallel the potential difference across each component is the same

Question 9

what is electrical charge

Answer 9

Electric charge is an amount of electricity that is held in or carried by something.
a current of one amp = 1 coulomb of charge flowing per second

Question 10

what is the equation for charge flow

Answer 10

q=lxt
charge flow =currentxtime

Question 11

What is resistance ?

Answer 11

Resistance tells us the potential difference required to drive a current through a component

Question 12

What is the equation for energy transferred?

Answer 12

E=QxV
Energy transferred (G) = charge flow (C) x potential difference (V)

Question 13

What is the equation for resistance?

Answer 13

R=V/I
Resistance=pd/current

Question 14

what is DC?

Answer 14

direct current produced from a cell

Question 15

what is an AC?

Answer 15

• Alternating current and an example is uk mains
• in uk AC frequency is 50Hz
  -PD is 230 volts

Question 16

what are benifits of AC?

Answer 16

• very easy to use a transformer to increase or decrease the pd

Question 17

what is the brown live wire used for?

Answer 17

-carries the alternating potential difference from the supply(230v)
-connected to the fuse in the plug

Question 18

what is the blue neutral wire used for?

Answer 18

completes the circuit and has a pd of 0 compared to the live wire

Question 19

what is the green and yellow safety wire used for?

Answer 19

-stops the appliances from becoming live

Question 20

what is the national grid?

Answer 20

the national grid consists of a system of transformers and high voltage cables

Question 21

what does a step up transformer do?

Answer 21

increase potential difference to several hundred thousand volts so less energy is lost within the power cables

Question 22

what is uncertainty

Answer 22

due to random error scientists cannot be certain of the accurate or true value of measurement

Question 23

how do we calculate uncertainty

Answer 23

range of values/2

Question 24

what is the equation that links power current and resistance

Answer 24

power=current^2 x resistance

Question 25

what is the resistance of an LDR like

Answer 25

-Resistance of an LDR is low in the light -Resistance changes depending on light intensity

Question 26

what happens to the ammeter in a circuit if resistance of the circuit decreases

Answer 26

-more current is allowed to flow through the circuit

Question 27

what happens to the voltmeter if the resistance of the component its reading decreases

Answer 27

-the voltmeter would get less share of PD -the reading of the voltmeter will decrease

Question 28

how should we change the circuit to give negative values for current and PD

Answer 28

reverse connections to the cell

Question 29

relationship between current and pd for a resistor at constant temp

Answer 29

directly proportional

Question 30

differences between AC and DC

Answer 30

-direct current is always in the same direction -alternating current changes direction

Question 31

when connecting to the uk mains why is it beneficial to use a low resistance cable

Answer 31

-lower potential difference across the cable -it is more efficient

Question 32

calculation for resistance

Answer 32

PD/current

Question 33

what is the resistance of resistors connected in parallel

Answer 33

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

Question 34

student increased the temperature of the thermistor. Explain how the current in the thermistor changed.

Answer 34

-the current increased -(because) the resistance (of the thermistor) decreased

Question 35

The heating element of the kettle was connected to the mains supply. Explain why the temperature of the heating element increased.

Answer 35

-electrons collide with particles in the heating element -which increases the (kinetic) energy of the particles

Question 36

measuring using a geiger muller tube explain why count rate of a radioactive sample is less then activity

Answer 36

-the source spreads radiation in every direction -the geiger muller tube only measures the radiation that passes through