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X1012 =Tera (T)
X109 =Giga (G)
X106 =Mega (M)
X10 =Kilo (K)
X103 =mili (m)
X106 =micra (µ)
X109 =nano (n)
X1012 =pico (p)
X1015 =femto (fm)

1. Current, Charge, Potential Difference, Resistance and Power:
· current = charge/time
· current measured in amps (A)
· current…

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· voltage measured using a voltmeter, a voltmeter must be attached in parallel. It also has
very high resistance to stop current flowing through it.
· When there is no internal resistance the EMF is equal to the potential difference.
· current is proportional to voltage ( I V) as…

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power cables that transfer electricity without wasting energy/power.
electronic circuits that are extremely fast as theres no resistance.

Electricity revision notes

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3. Components and their characteristics:

I/V graphs:
· The shallower the gradient the greater the resistance
· A curve shows the resistance is changing.

· a cell is a source of electrical energy and a battery is a
combination of cells.

· a diode allows the current to…

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I/V graph for a diode:
To investigate the characteristics of a diode,
one set of measurements are taken with the
diode forward biased. Then another set taken
in reverse biased. This gives you the I/V
graph to the right.

·a resistor is a component designed to have certain resistance…

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Investigating the characteristics of different components (in order to draw the I/V graph):
· in order to measure the variation of current with pd for a component use a potential
divider (vary from 0 pd) or variable resisistor (vary current to a min.)

Potential divider circuit.
Variable resisitor circuit.

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· Energy is conserved. Energy transferred to a charge is EMF and energy transferred from a charge is
potential difference. Total emf areound a series circuit equals the sum of the pds across each
· In a series ciruit, the pd splits across each component so the voltages across…

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6. EMF and internal resisistance:

· r = internal resistance
· R = external resistor
· E = EMF the terminal PD is less that then EMF due to the internal resistance but if there
was no internal resistance then PD would equal the EMF
· terminal pd, IR, =…

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Maximum power is delivered to the load when the load resistance is equal to the internal resistance of the

Measuring the internal resistance:
y2y1 / x2x1 > V2V1 / I2I1 = r
· first measure the pd across the
terminals of a cell, by connecting a
high resistance voltmeter…

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7. Circuit Calculations including Emf and cells (batteries):

· cell current = cell emf / total circuit resistance

· working out pd for each resistor, start with resistors in series with the cell which therefore passes
the same current as the cell current:
Pd across each resistor
in series with…


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