Electrons and Electricity Flashcards
What are the 2 types of current?
Direct current (DC) and Alternating current (AC)
What is current?
The flow of electrons caused by a potential difference
Describe the flow of electrons in direct current?
In direct current the electrons flow in one direction through a conductor.
Describe the flow of electrons in alternating current?
In alternating current the electrons change direction back and forth in the conductor.
What is a source of D.C.?
Chemical cells and batteries
What’s a source of A.C. ?
Mains electricity
Alternating current definition
A current which changes direction and instantaneous value with time
What is the AC equivalent of DC voltage and current?
The root mean squared (Vrms/Irms)
Do you used peak or rms in ohms law calculations surrounding AC/DC supplies?
rms values
What equipment do you use to measure the frequency and peak voltage of an AC supply?
An oscilloscope
What the DC equivalent of a 2Vrms AC supply?
2V
EMF definition
The electromotive force is the number of joules of electrical energy given to each column of charge that passes through the source
What is a property of an ideal cell?
One without internal resistance
What are lost volts?
The potential difference developed across the internal resistance of a cell in a circuit
What is the terminal potential difference?
The potential difference across all over terminals in a circuit
The larger the current, the ______ the value of lost volts and the ________ the terminal potential difference
Higher, Lower
What is Vlost when the current is zero?
V lost is 0
What is the terminal potential difference when current is zero?
Equal to the EMF of the battery/cell
What is an open circuit?
A circuit where no current is flowing (and it’s terminal voltage is equal to EMF)
What is a short circuit?
When there is only the voltage supply in a circuit (so current and Vlost is maximum)
What is the gradient of a voltage/current graph equal to?
The negative of the internal resistance (m = -r)
What is a capacitor?
An electronic device that can store charge and energy in a DC circuit
What is the relationship between charge stored and potential difference in a capacitor?
The charge stored is proportional to the potential difference
How do we find the energy stored in a capacitor using a change-potential difference graph?
By calculating area under the graph as it is equal to the energy stored
What happens to the current in a capacitor circuit when the capacitor is being discharged?
The current flows in the opposite direction going from - Imaximum to 0
How can you increase the charging time of a capacitor?
Increasing the resistance of the circuit will limit the size of the current, slowing down charging
