P2 electricity

Question 1

what are Kirchhoff’s laws

Answer 1

1.if a current splits off into several others those others must add up to make whats been split eg:10 is split into 6 and 4

2.The sum of voltages of each component on a loop of a circuit equals the voltage of the cell

Question 2

What is the equation for voltage (Ohm’s law)

Answer 2

V=IR or Voltage=current * resistance

Question 3

What does the voltmeter do

Answer 3

measures the potential difference between two point of a circuit

Question 4

what does an ammeter do

Answer 4

measures the current through a point on a circuit

Question 5

what does a resistor do

Answer 5

resists the flow of current through a point, all components that use power have resistance (e.g. bulb)

Question 6

whats a variable resistor, why are they useful?

Answer 6

a resistor where you can change what the resistance is

They allow you to alter the current through a circuit

Question 7

what’s current measured in

Answer 7

amps

Question 8

what’s voltage/ potential difference measured in

Answer 8

volts

Question 9

what’s resistance measured in

Answer 9

ohms

Question 10

what is charge measured in

Answer 10

colombs

Question 11

what is a light resistant diode

Answer 11

a resistor that alters depending on light

Question 12

what is the equation for charge flow

Answer 12

current * time

Question 13

a straight line through a voltage current graph means what?

Answer 13

resistance is constant

Question 14

what is an ohmic resistor

Answer 14

a resistor in which the current is directly proportional to the voltage at a constant temperature
-this means resistance remains the same as current changes

Question 15

name 2 differences between series and parallel circuits

Answer 15

-total voltage in series circuit is shared through components while in parallel the total voyage inputted is the same at every component
-same current through each component but in parallel total current from the power supply is the sum of all the currents from the components

Question 16

equation for power

Answer 16

P=IV

Question 17

name 2 features of direct current

Answer 17

-has a voltage that is always positive or negative (constant direction)
-type of current supplied by batteries

Question 18

name 2 features of alternating current

Answer 18

-voltage changes from positive to negative (alternating direction) with some frequency
-type of current in mains electricity

Question 19

what is mains voltage and frequency in the Uk

Answer 19

230V and 50Hz

Question 20

what colours are the live, earth and neutral wires

Answer 20

brown, yellow and green, blue

Question 21

what does the earth wire do

Answer 21

it acts as a safety wire which stops the exterior of the appliance to become live

Question 22

how does an electric shock work

Answer 22

-live wire between wall and switch is still at an alternating potential
-needs path for electricity to flow through
-if someone touches the wire it creates a potential difference from wire to the earth and flows through you into the ground

Question 23

what is the equation for efficiency

Answer 23

useful energy transfer/total energy transfer

Question 24

what is the equation for energy transferred

Answer 24

power * time

Question 25

how does electricity travel from the power station to the houses

Answer 25

-from the power station it uses a step up transformer to increase voltage as it goes through the cables which reduces current and therefore heating and also energy loss
-then steps down for household use as it would otherwise be to dangerous

Question 26

how does an object become charged after rubbing against another

Answer 26

-one material will need electrons the other will want to get rid of electrons
-when rubbed against each other electrons will attract
-this will make one object positive and the other negative