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Electricity
Electricity

The flow of electrons around a complete circuit

Conventional current
As electricity is the flow of electrons, which are negatively charged, the flow of the current
is from negative to positive
However before this was discovered the opposite was thought. Therefore conventional
current is used despite it being…

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This is the energy transferred to the current per unit of charge. This is how much energy is
transferred to the electrons. This can take into account resistance, such as that from the battery
which will decrease the charge in the circuit.

Rules in a circuit

As charge flows through…

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In an exam, if there is a diode in the circuit and a current is flowing, the potential difference across
the diode is always 0.6 V




In thermistors, as the temperature increases, the
resistance of the component decreases. These
components are made of intrinsic semiconductors
(not metal) and have a…

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across it, and so the resistance is zero. This is true until the temperature exceeds critical, which
results in the conductor gaining resistivity rapidly.

Uses of these super conductors include:

High power electromagnets

Power cables- as they allow energy to be transferred efficiently as no energy will be lost through…

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E
=Q

Terminal Potential difference

"The electrical energy per unit of charge delivered to the circuit"

This is given by:

T erminal pd = I R

The lost voltage due to the internal resistance of a battery is given by:

Lost pd = I r

Therefore, EMF can be written…

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2
This is worked out through P = I 2R which when subbed into P = VR can be written as the
following:
2
P = (R+r)2
R

gives the current.
This works as I = R+r


Maximum power is delivered to the load when the load resistance is equal…

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Supplying a variable pd

Length of wired with a sliding contact is used. This can be used for audio volume controls and to
vary the brightness of light bulbs.

Sensor circuits

A sensor circuit produces an output pd which varies when a physical variable changes

Temperature sensor

This consists of…

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Heating effect


P=I2R

Power changes as current changes. Maximum power occurs where the peak current is supplied.

Root mean square

This is the value of direct current that would produce the same heating effect as the alternating
current at the same resistance.

Root mean square is:
1V
V rms =…

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