an instrument used to measure the current flowing in an electric circuit and is always connected in series. An ideal ammeter should have extremely low resistance.
defined in terms of the force per unit length between parallel current-carrying conductors.
have a low electrical resistance and are therefore able to carry an electric current withour much energy dissipation as heat.
flows from the positive to negative terminal.
the rate at which charge flows past a given cross-section.
electric potential difference
The work done per unit charge to move a small positive charge between the two points.
the ratio of the potential difference across the material to the current that flows through it. The units of resistance are volts per ampere (V A^-1). However, a separate SI unit called the ohm Ω is defined as the resistance through which a current of 1 A flows when a potential difference of 1 V is applied.
electromotive force (emf)
the work per unit charge made available by an electrical source.
flows from the negative to the positive terminal.
the energy acquired by an electron as a result of moving through a potential difference of one volt.
the electrons are held tightly by the atomic nuclei and are not as free to move through a material. They can accumulate on the surface of the insulator but they are not conducting.
the resistance inside a source of electrical energy.
this is energy that is usually associated with an electric current and that is sometimes referred to incorrectly as electricity.
the energy consumed when 1 kW of power is used for one hour.
the current is directly proportional to the potential difference at a constant temperature
is used to measure the voltage drop across part of an electric circuit and is always connected in parallel. An ideal voltmeter has a high amount of resistance.
(negative temperature coefficient) the resistance decreases when the temperature rises and theytherefore pass more current.
light dependant resistor (LDR)
is a photo-condutive cell whose resistance changes with the intensity of the incident light.