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Slide 1

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P6 Electricity for Gadgets
Charging (g)…read more

Slide 2

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Diodes only let current flow freely in one
direction, because there is very high resistance
in the other direction.
- Resistor protects it from getting brunt by a
large current.
Single: Changing AC into DC = not a constant
value but the current is always in the same
- This produces a half-wave rectified output.
Voltage = 0.6V + to let is start working.
Reversed biased: battery is reversed = no
current…read more

Slide 3

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Diode Resistance
A silicon is a device that allows current to flow
through it in one direction only. A current-voltage
characteristic can be drawn for a diode by plotting
the current through the diode against the voltage
across the diode. A silicon diode is made of two types
of silicon:
n-type, which contains extra electrons (so has extra
negative charge carriers)
p-type, which has holes where there should be
electrons (so the holes are like positive charge
A diode is forward biased in a circuit when the n-type
is connected to the negative terminal of the battery.
Current can flow because: the electrons can flow
towards the holes and the holes can flow towards the
If the diode is reverse biased (backwards), the current
can't flow. This is because the electrons seems to drop
into the holes and are unable to get past the layer…read more

Slide 4

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Full-wave rectification
To get full wave rectification you need a
bridge circuit, with 4 diodes. in a bridge
circuit the current always flows through
the component in the same direction and
the output voltage always has the same
sign…read more

Slide 5

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A capacitor stores charge that can be
discharged later. When current flows in a
circuit containing an uncharged capacitor,
the charge is stored on the capacitor and its
pd increases. When a charged capacitor is
connected to a conductor, the capacitor
behaves like a battery. This capacitor
dicharges, sending its stored current through
the conducter.
When a charged capacitor is connected to a
conductor, the flow of current from the
capacitor to the conductor isn't steady.
Instead the current flow decreases as the
charge on the capacitor decreases.
As the charge on the capacitor decreases, the…read more

Slide 6

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Simple Smoothing
A capacitor connected across a varying
voltage supply produces a more constant
(smoothed) output. This is useful for
devices that need a more constant voltage
supplied to them.
A capacitor smoothes the output by
discharging when the pd falls to a certain
level, putting more charge into the circuit.
This boosts the current so that it remains
When the pd in the circuit is high enough,
the capacitor charges up again. It remains
charged until the pd falls and the capacitor…read more

Slide 7

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