mains electricity

Question 1

How can you use a variable resistor to increase current in

Answer 1

• Set the variable resistor to a lower resistance

- increasing current

Question 2

Importance of connecting fuse/switch to live wire

Answer 2

• overcurrent = fuse wire melts
• circuit will break + stop running current through live wire
• provides a method to stop current flowing into appliance

Question 3

Direct vs alternating current

Answer 3

• current flowing in one direction (cell/battery)

- current changes direction continuously as time passes (mains electricity)

Question 4

Describe between thermistors and resistance

Answer 4

• When temp increases resistance decreases vice versa

Question 5

Give 2 advantages of using CB’s over fuses

Answer 5

• More sensitive
• Easier to reset
• Dont need to be replaced

Question 6

Series

Answer 6

• Same current flows through all components
• Voltage across components isnt the same - shared
• Total V is = total sum of V across each component = R1 + R2 = Rt

Question 7

What is double insulation

Answer 7

• Casing of appliance made of plastic
• plastic is an insulator
• disallows electric current flow
• EW cannot touch the casing
• prevents electrocution

Question 8

How does using a thermistor affect temp changes

Answer 8

• As temp increases

- resistance decreases

Question 9

How does changing the resistance in the circuit change the current

Answer 9

• Current is vice versa to resistance
• increasing resistance will decrease current
• A higher resistance makes it harder for electrons to pass through (current) thus reducing current

Question 10

How does a LDR work?

Answer 10

• resist. of a LDR varies w light

- as light intensity increases resistance decreases vice versa

Question 11

Parellel

Answer 11

• Current flowing in a junction= current leaving
  Voltage across each branch is the same
• advantageous as if one lamp breaks others till work//can control diff lights at same time

1/Rt= 1/R1 + 1/R2 - flip it for answer

Question 12

what isnt required if an appliance is double insulated

Answer 12

• Earth wire
• EW is connected to the casing of the material
• If the plastic is acting as an insulator
  EW cant pass current through to the ground

Question 13

Live wire vs neutral wire and their colors

Answer 13

• Live supplies V to circuit + forms the current within, considered a dangerous wire (brown/red)
• Neutral carries away current + completes circuit hence current can flow (blue)

Question 14

How does earth wire ensure safety and color

Answer 14

• Connected metal casing of device
• Provides low reist. path to ground
• if fault occurs EW allows large currents through live wire to flow to ground (green n yellow)

Question 15

relationship between resistance and current in a circuit

Answer 15

• increasing resistance decreases current
• electrical current is flow of electrons so increasing resist. makes it harder for electrons to pass through + reducing current

Question 16

relationship between thermistors and resistance + LDR works

Answer 16

• temp increase —> resistance decreases
• the resis of LDR varies w light
• as light intensity increases, resistance decreases

Question 17

series circuit

Answer 17

• all components are connected in same loop
• different voltage across components
• total V = sum of all V across each components
• ammeter connected in series

Question 18

parallel circuit

Answer 18

• the components are on diff loops
• current in = current out
• voltage is the same across all components
• in domestic - can control more than one light, if one bulb quits the others work

Question 19

how to find resistance of wire at constant temp

Answer 19

• instrument to measure resistance
• maintain constant temp (switch on and off)
• use of V=IR
• repeat/avergaing
• use of graph