Current electricity (13)

Question 1

Resistance, R

Answer 1

defined by the equation R=V/I . Measured in ohms, Ω. The resistance of a conductor is the opposition of the conductor to electric current flowing through it.

Question 2

Electrolyte

Answer 2

a conducting solution, usually containing positive and negative salt ions dissolved in water.

Question 3

Electromotive force (emf)

Answer 3

the amount of electrical work done per unit charge by a power supply such as a cell in an electrical circuit. The power supply transfers the other forms of energy, such as chemical energy into electrical energy. The unit is the volt, V.

Question 4

Superconductor

Answer 4

a material whose resistance drops to zero below a specific temperature, called the critical temperature.

Question 5

Electrical characteristic

Answer 5

a graph (usually I-V) that illustrates the electrical behaviour of the component.

Question 6

Ohmic conductor

Answer 6

the current flowing through an ohmic conductor is proportional to the pd applied across it.

Question 7

Non-ohmic

Answer 7

a non-ohmic component is a component that does not obey Ohm’s law; i.e. the current is not proportional to the potential difference applied across it.

Question 8

Thermistor

Answer 8

a component whose resistance varies with temperature. Many thermistors used in electrical circuits have a negative temperature coefficient (ntc), meaning that their resistance decreases with increasing temperature.

Question 9

Intrinsic

Answer 9

an intrinsic property of a material is a property of the material itself, independent of other factors. E.g. resistivity.

Question 10

Resistivity

Answer 10

the resistivity of a substance is the intrinsic resistance of the material that the substance is made from; it is independent of the dimensions of the substance. Resistivity also varies with temperature, although the resistivity of metals changes only gradually with temperature.