Electricity Flashcards
Define an electric current
The rate of net flow of any electrically charged particles
Define the Coulomb
1 coulomb is equal to the charge that passes when a current of 1 ampere flows for a time of 1 second
Define the mAh
If a current of 1 mA passes a point in the time of 1 hour the total charge is 1 mAh
Define potential difference
The energy transferred per unit charge from electrical to other forms
Define resistance
Ratio of potential difference across a component to the current through it
State ohm’s law
for metallic conductor, the potential difference across it is proportional to the current through it, given all other physical conditions are constant i.e temperature
Describe the cause of electrical resistance
The current through a component has a heating effect. As the temperature increases the ions vibrate more. The is an increase in the frequency of electron-ion collisions hence the resistance increases
What is a superconductor?
A material that has zero resistance below the critical temperature. Therefore extremely large currents can flow without a loss in thermal energy.
Define power
The rate of energy transfer or work done
Define the kilowatt-hour
The energy transferred when an appliance of power 1kW operates for 1 hour
Kirchhoffs first law
Sum of the currents entering the junction equals the sum of the currents exiting the junction
Kirchhoffs second law
In any closed loop, the sum of emfs is equal to the sum of potential difference drops in that loop
Define emf
The electrical energy per unit charge provided by the battery
Define internal resistance
internal resistance of a source is the loss of potential defference per unit current, when current pass through the source due to a resistance of the source itself
Define terminal pd
The electrical energy per unit charge delivered by the source to the external circuit
