What happens to a charge in an electric field?
It experiences a force
What happens when a charge is moved in an electric field?
Work is done
What is the potential difference between 2 points?
The work done moving 1C of charge between the points
If 3J of work is done moving 1C between 2 points what is the pd between them?
What are the three main equations for electric fields?
What is EMF ?
The energy supplied to each coulomb of charge passing through the source
What are the main formula for EMF
1) E= V + Ir
2) E= I(R+r)
4) lost volts = Ir
What is an open circuit?
1) A source of EMF connected only to a voltmeter
2) As there is no current there are no lost volts
3) The voltmeter can read the actual EMF
What are lost volts?
Voltage across the internal resistance
What is terminal pd?
The voltage actually available at the output of a supply
What is a load resistor?
Any external resistance
What is a short circuit current?
1) When there is no external resistance R=0
2) Current = EMF÷internal resistance
If a wheatstone bridge is balanced what is the voltage between the two voltage dividers?
What is Capacitance?
How much charge can be stored per volt
What is the relationship between the charges stored on 2 plates and the voltage between them?
As on increases so does the other
What is the effect of frequency on resistors and capacitors?
No effect on resistors
Capacitors - current increases with frequency
What effect do capacitors have on d.c and a.c signals?
Allows a.c to pass
What are op-amps used for?
Increase the voltage of a signal
For an ideal op-amp what is the condition for current?
Infinite input resistance
No input current
For an ideal op-amp what is the condition for voltage?
No pd between the input terminals
Both input terminals at the same pd
What type of op-amp inverts the input signal?
What type of op-amp amplifies the difference between the inputs?
When do op-amps become saturated?
When the maximum values of it's power supply have been reached
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