Electricity, work and energy revision

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  • Created on: 15-05-14 18:32
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Work, power and elect ricity
Work (done) = force x distance
Work = energy transferred
Kinetic energy = ½ x mass x speed 2 Energy- Joules (J)
Force- Newtons (N)
Gravitational potential energy = weight (or mass x g) x height Power- Watts (W)
Voltage- Volts (V)
Work/energy = power x time Current- Amperes/amps (A)
Charge- Coulombs (C)
Energy = voltage x current x time (E=VIt or E=Pt or E=VQ) Resistance- Ohms ()
Voltage = current x resistance (V=IR)
Charge = current x time (QIt)
Power = current x voltage (P=IV)
Notes about work and energy
- As energy is never lost, only transferred, all gravitational potential energy (GPE) of a falling
object becomes kinetic energy (N.B. Energy transferred = work)
- Power is the rate of doing work/transfer of energy
-An electric current is a flow of
negatively charged ions
Symbol -Current is rate of flow of charge
Current I -Voltage is energy transferred per
coulomb of charge
Charge Q
-Voltage between 2 points is
Time t (lowercase) number of joules converted per
Voltage V coulomb of charge that flows
between them
Energy E
-Electrons carry the charge
Resistance R -Higher resistance smaller
Power P current
-N.B. In parallel (current has more
than one path way to flow), if one
component breaks, the others stay on- so these circuits are
better for domestic lighting, so if one bulb breaks, the
others won't all switch off too

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Current and voltage in circuits
-Current in series circuit is the same everywhere
and depends on voltage and number of components
-Voltage across battery in a series circuit is equal
to sum of voltage across components
-Current across battery in parallel circuit is equal
to sum of current across branches (also, more
branches more power drawn from battery)
-Voltage in parallel circuit is the same everywhere
- Components offer resistance to flow of charge.…read more


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