Circuits Definitions Flashcards
Conductors
A material that allows the flow of electrical charge. Good conductors have a larger amount of free charge carriers to carry a current.
Conservation of charge
The total charge in a system cannot change
Conventional current
The flow from positive to negative terminal in a cell or battery, used to describe the current in a circuit
Electric current
the rate of flow of charge
electron flow
the opposite direction to conventional current flow. Electrons flow form negative to positive terminal in a cell or battery
elementary charge
the smallest possible charge, equal to the charge of an electron
insulator
A material that has no free charge carriers and so doesn’t allow the flow of electrical charge.
Kirchhoff’s First Law
A consequence of the conservation of charge. The total
current entering a junction must equal the total current leaving it.
Mean Drift Velocity
The average velocity of an electron passing through an
object. It is proportional to the current, and inversely proportional to the number of charge carriers and the cross-sectional area of the object
Quantisation of Charge
The idea that charge can only exist in discrete packets
of multiples of the elementary charge.
Semiconductors
A material that has the ability to change its number of charge carriers, and so its ability to conduct electricity. Light dependent resistors and thermistors are both examples.
Diode
A component that allows current through in one direction only. In the correct direction, diodes have a threshold voltage (typically 0.6 V) above which current can flow.
Electromotive Force
The energy supplied by a source per unit charge passing
through the source, measured in volts.
Filament Lamp
A bulb consisting of a metal filament, that heats up and glows to produce light. As the filament increases in temperature, its resistance increases since the metal ions vibrate more and make it harder for the charge carriers to
pass through.
LDR
A light sensitive semiconductor whose resistance
increases when light intensity decreases.
Ohmic conductor
A conductor for which the current flow is directly proportional to the potential difference across it, when under constant physical conditions.
Ohm’s Law
The current and potential difference through an ohmic conductor held under constant physical conditions are directly proportional, with the constant of proportionality being resistance.
Potential Difference
The difference in electrical potential between two points in a circuit. It is also the work done per coulomb to move a charge from the lower potential point to the higher potential point. It is measured in Volts.
Power
The rate of energy transfer in a circuit. It can be calculated as the product of the current and the potential difference between two points. It is measured in Watts.
Resistance
A measure of how difficult it is for current to flow through a material.
Resistivity
A measure of how difficult it is for charge to travel through a material. It is proportional to the object’s resistance and cross-sectional area, and inversely proportional to the object’s length. It is measured in Ohm metres.
Conservation of Energy
Energy cannot be created or destroyed - it can only be
transferred into different forms.
Internal Resistance
The resistance to the flow of charge within a source. Internal resistance results in energy being dissipated within the source.
Kirchhoff’s Second Law
A consequence of the conservation of energy. The sum
of the voltages in any closed loop must equal zero.
Lost Volts
The difference between a source’s emf and the terminal voltage. It is equal to the potential difference across the source’s internal resistance.
Potential Divider
A method of splitting a potential difference, by connecting two resistors in series. The total potential difference is split in the ratio of their resistances.
Resistors in Parallel
The potential difference across resistors connected in
parallel is identical for each resistor. The current is split between the resistors. The total resistance is equal to the inverse of the sum of the inverses of the resistances of the resistors.
Resistors in Series
The current through resistors connected in series is identical for each resistor. The potential difference is split in the ratio of their resistances. The total resistance is equal to the sum of the resistances of the resistors.
Terminal PD
The potential difference across the terminals of a power source. It is equal to the source’s emf minus any voltage drop over the source’s internal resistance
