Dear student,
1)
Electric potential is the electric level at a particular point.
The potential difference between two points in an electric field is defined as the amount of work done in moving a unit positive charge from one point to another point.
Potential difference = work done/quantity of charge transferred
V = W/Q
Units: 1 V = 1 J/1 C
2)
Resistance
The property of conductor due to which it opposes flow of current is called resistance. During the electric flow the electrons collide with other electrons and also with the atoms and ions present in the conductor causing some obstruction to the flow of electrons. A resistor is used to control the current.
Ammeter
An ammeter is used to measure the electric current in the circuit. Ammeter should be connected in series in the circuit.
3)
Voltmeter is used to measure the potential difference across the device. It is to be connected in parallel to the device.
A galvanometer is a type of ammeter. It is used to measure electric current. It is an electromechanical transducer that produces a rotary deflection (pointer) in response to current flowing through a coil in a constant magnetic field.
Regards.