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Definitions for Topic 5 - Electricity and Magnetism: 5.1 - Electric fields 5.2 - Heating effects of electric currents 5.3 - Electric cells 5.4 - Magnetic effects of electric currents
Coulomb (the unit of charge)
The charge is transported by a current of one ampere in one second. Unit: As
Electric field strength
The electric field strength at a point is the force per unit charge experienced by a small positive point charge placed at that point
Drift speed
The speed at which charge carriers move along a conductor
Potential difference (pd)
Potential difference between two points I the work done when moving a unit of charge between the points
Electronvolt (eV)
The energy gained by an electron when it moves through a potential difference of one volt
1.6*10^-19 J
Resistance
The opposition to charge flow in an electrical circuit
Ohm’s law
The current through a conductor between two points is directly proportional to the potential difference between the two points
The resistance is constant as the current changes (ohmic conductors)
Resistivity
A fundamental property of a material that shows how well the material conducts electricity
Low resistivity means that the material is a good conductor
Kirchhoff’s first law
The total charge flowing into a junction is equal to the total charge flowing out
Kirchhoff’s second law
The total electromotive force around a closed circuit loop is equal to the sum of the potential differences around the loop
Electric cell
An electric cell is a device that converts chemical energy into electrical energy = the cell is discharging
When electrons pass through a cell, chemical energy -> electrical energy
When electrons pass through a resistor, electrical energy -> other forms of energy
Electromotive force (emf)
The work done per unit charge when moving charge between the terminals of a cell
Internal resistance
Resistance of components within the cell itself, leading to energy losses in the cell
Right-hand corkscrew rule
When our right thumb is pointing in the direction of the conventional current, our curling fingers show the direction of the magnetic field
