A battery is a device that converts chemical energy into electrical energy. It typically consists of one or more electrochemical cells connected together to produce a voltage and supply power to electrical devices.
Emf stands for electromotive force, which is the amount of electrical energy that a battery can supply to an external circuit. It is measured in volts (V) and is essentially the force that pushes the electrons through the circuit.
Emf is the potential difference between the two terminals of a battery when it is not connected to a circuit, while voltage is the potential difference between two points in a circuit. Emf is the maximum voltage a battery can produce, while voltage is the actual potential difference experienced in a circuit.
Resistance is a measure of the opposition to the flow of electric current in a circuit. It is caused by factors such as the material of the wire, its length, and its cross-sectional area. Resistance reduces the amount of current that can flow through a circuit and is measured in ohms (Ω).
Voltage can be calculated by using Ohm's Law, which states that voltage (V) equals current (I) multiplied by resistance (R). This can be written as V = IR. Voltage can also be calculated by using a voltmeter to measure the potential difference between two points in a circuit.