mains electricity Flashcards
How can you use a variable resistor to increase current in
- Set the variable resistor to a lower resistance
- increasing current
Importance of connecting fuse/switch to live wire
- overcurrent = fuse wire melts
- circuit will break + stop running current through live wire
- provides a method to stop current flowing into appliance
Direct vs alternating current
- current flowing in one direction (cell/battery)
- current changes direction continuously as time passes (mains electricity)
Describe between thermistors and resistance
- When temp increases resistance decreases vice versa
Give 2 advantages of using CB’s over fuses
- More sensitive
- Easier to reset
- Dont need to be replaced
Series
- 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
What is double insulation
- Casing of appliance made of plastic
- plastic is an insulator
- disallows electric current flow
- EW cannot touch the casing
- prevents electrocution
How does using a thermistor affect temp changes
- As temp increases
- resistance decreases
How does changing the resistance in the circuit change the current
- 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
How does a LDR work?
- resist. of a LDR varies w light
- as light intensity increases resistance decreases vice versa
Parellel
- 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
what isnt required if an appliance is double insulated
- 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
Live wire vs neutral wire and their colors
- 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)
How does earth wire ensure safety and color
- 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)
relationship between resistance and current in a circuit
- increasing resistance decreases current
- electrical current is flow of electrons so increasing resist. makes it harder for electrons to pass through + reducing current
relationship between thermistors and resistance + LDR works
- temp increase —> resistance decreases
- the resis of LDR varies w light
- as light intensity increases, resistance decreases
series circuit
- all components are connected in same loop
- different voltage across components
- total V = sum of all V across each components
- ammeter connected in series
parallel circuit
- 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
how to find resistance of wire at constant temp
- instrument to measure resistance
- maintain constant temp (switch on and off)
- use of V=IR
- repeat/avergaing
- use of graph
