Electricity Flashcards
What is current
The rate of flow of charge round an electric circuit
What happens to the current if the resistance is higher
The higher the resistance the lower the current for a fixed p.d
Equation for charge
Q=It
Equation for p.d
V=IR
V = E/Q
What happens to the resistance in Ohmic conductors as current changes
It doesn’t change
What is the IV characteristics of an ohmic conductor
Current is directly proportional to the p.d
What is the IV characteristic of a filament lamp
‘F’ like
As temperature increases, resistance increases therefore less current can flow hence the curve
What is the IV characteristic of a diode
Exponential like
Current will only flow through the diode in one direction
The diode has a very high resistance in the opposite direction
What is the IV characteristic of a Light-dependent resistor
Decreasing resistance as light increases
Used in automatic night lights
What is the IV characteristic of a Thermistor
Decreasing resistance as temperature increases
Used in car engine temperature sensors and electronic thermostats
What is the equivalent resistance in parallel circuits
The resistance of one resistor/ The no. of resistors
How does the no. of identical resistors affect a series circuit
Increases resistance
How does the no. of identical resistors affect a parallel circuit
Decreases resistance
What is the frequency of A.C mains supply
50hz
What colour and what does the neutral wire do
Blue
Completes the circuit and a current flows through it
It has around 0V
What colour and what does the earth wire do
Green and yellow
For protecting the wiring and stops the appliance casing from becoming live
What colour and what does the live wire do
Brown
Provides the alternating p.d (230v) from the mains supply
What does the earth wire do if you touch the socket
Provide an alternative route and lower resistance path into the earth
Equation for power
Power = E/t
Power = IV
Power = I^2R
What is the national grid
A giant system of cables and transformers that covers the UK and connects power stations to consumers
What does the national grid use in terms of p.d. and current
High p.d and low current
You’d lose loads of energy as the wires heat up
More efficient
How are input power and output power linked in transformers
P1V1 = P2V2
What happens when 2 insulating materials are rubbed together
Charged electrons will be scraped off one and dumped onto the other
This will leave the materials electrically charged - positive and negative
What happens when an electric charge builds up on an object
The p.d between the object and the earth increases
If it increases to a large enough point then electrons can jump across the gap
They can also jump to any other earthed conductor
