The grade 11, chapter 11, electric circuits presentation

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11. Electric circuits
Physics
Grade 11

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Ohm's Law
Ohm’s Law states that the amount of current through a conductor, at constant temperature, is
proportional to the voltage across the resistor. Mathematically we write
where I is the current through the conductor, V is the voltage across the conductor and R is
the resistance of the conductor.
I=
V
R

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Ohm's Law and conductors
Conductors that obey Ohm’s Law are called ohmic conductors; those that do not are called
non-ohmic conductors.

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Series and parallel circuits
The equivalent resistance of
resistors in parallel (Rp
) can be
calculated as follows:
The equivalent resistance of
resistors in series (Rs
) can be
calculated as follows:
Rs=R1+R2+R3+... 1
Rp
=
1
R1
+
1
R2
+
1
R3
+...

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More on series and parallel circuits
IT=I1=I2=I3 VT =V 1+V2+V3
In a series circuit the amount of current is the
same through any component in the circuit.
And the total voltage of the circuit has to be
equal to the sum of the voltages over all
three resistors. This can be expressed as
(assuming three resistors):
In a parallel circuit the voltage is equal
across all components in the circuit. And all
the currents through each resistor must add
up to the total current in the circuit. This can
be expressed as (assuming three resistors):
VT =V 1=V 2=V 3 IT =I1+I2+I3

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Electrical power and energy
Electrical power is the rate at which electrical energy is converted in an electric circuit.
Power (P) is measured in watts (W).
Using Ohm's Law we can find two alternate forms of this expression to calculate power:
The electrical energy dissipated is and is measured in joules (J).
P=I⋅V
P=I2
⋅R P=
V 2
R
E=P⋅t

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