year 1 electricity

define electromotive force (emf)

the work done per unit charge to move a charge around a circuit

define potential difference

the work done by an electron per unit charge to move from one point in the circuit to another

conventional current flow?

positive to negative

define current

the rate of flow of charge

electron flow?

negative to positive

what is a diode?

a component that only allows current to flow through in one direction.

define internal resistance

the unavoidable resistance any power source will have that makes it harder for current to flow through the source. it causes energy to be dissipated in the source.

kirchhoffs first law ?

the total current entering a junction is equal to the total current leaving it

kirchoffs second law?

the sum of EMF in any loop of the circuit is equal to the sum of potential differences of each component

define power and its units

the rate of energy transfer (watts)

define resistance

a measure of how difficult it is for current to flow in a circuit or component. opposition to flow of charge

define resistivity

a measure of how difficult is it for charge to travel through a specific material.

what is a semiconductor

materials that change their resistance depending on external conditions

what is an ohmic conductor

the current flowing through is directly proportional to the potential difference between each end of the conductor (at constant temperature)

ohms law?

electric current is directly proportional to potential difference and inversely proportional to resistance (at constant temperature)

how is current split in a parallel circuit?

the current is split between the branches

how is current split in a series circuit?

current is the same across all components

how is potential difference split in a parallel circuit

potential difference over each loop is the same

how is potential difference split in a series circuit?

potential difference is split between components depending on their resistance.

what is terminal potential difference?

the actual potential difference across the terminals of a power source. it is the EMF minus the lost volts due to the sources internal resistance

what is a voltmeter?

a device used to measure the potential difference between two points on a circuit, ideally it has infinite resistance so no current can pass through

what is a superconductor?

materials with zero resistivity at below a critical temperature

2 examples of semiconductors

thermistors and LDRs

describe the IV characteristic of a filament bulb

as current increases, temperature increases, causing the metal ions to vibrate with more kinetic energy, making it harder for charge carries to pass through so resistance increases.

why is terminal potential difference never the same as the EMF value?

energy is dissipates within the source due to the cells internal resistance