GENERAL PHYSICS 2 – 4th Quarter
LESSON 1: OHM’S LAW
ROMMEL ANTONIO
MARCH 21, 2022
I.
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ELECTRICAL CIRCUIT
A system of conductors and components forming a
complete path for current to travel.
Properties of an electrical circuit includes:
o
Voltage = Volts (V)
o
Current = Amps (A)
o
Resistance = Ohms (Ω)
A.
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SITUATIONAL:
When the faucet (switch) is off, is there any pressure
(voltage)? YES = Pressure (voltage) is pushing
against the pipe, tank, and the faucet.
When the faucet (switch) is on, is there any pressure
(voltage)? YES = Pressure (voltage) pushes flow
(current) through the system.
CURRENT
The flow of electric charge
Measured in Amperes (A)
SITUATIONAL:
When the faucet (switch) is off, is there any flow
(current)? NO
When the faucet (switch) is on, is there any flow
(current)? YES
Figure 2. Voltage in a Circuit
C.
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RESISTANCE
The opposition of current flow
Measured in Ohms (Ω)
SITUATIONAL:
What happens to the flow (current) if a rock gets lodged
in the pipe? Flow (current) decreases.
Figure 1. Current in a Circuit
i.
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Current Flow
Conventional Current
o
It assumes that the current flows out of the
positive side of the battery, through the circuit,
and back to the negative side of the battery.
o
This was the convention established when
electricity was first discovered, but it is
incorrect.
Figure 3. Resistance in a Circuit
II.
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Current in a resistor varies in direct proportion to the
voltage applied to it and is inversely proportional to the
resistor’s value.
The mathematical relationship between current, voltage,
and resistance.
Electron Flow
o
This is what actually happens.
o
The electrons flow out of the negative side of
the battery, through the circuit, and back to the
positive side of the battery.
B.
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OHM’S LAW
VOLTAGE
The force (pressure) that causes current to flow
Measured in Volts (V)
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EXAMPLE 1: The flashlight shown uses a 6-volt battery and
has a bulb with a resistance of 150 Ω. When the
flashlight is on, how much current will be drawn from
the battery?
D.
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ELECTRICAL POWER IN CIRCUITS
Electrical Power (P) in a circuit is the rate at which
energy is absorbed or produced within a circuit.
A source of energy such as a voltage will produce or
deliver power while the connected load absorbs it.
Light bulbs and heaters for example, absorb electrical
power and convert it into either heat, or light, or both.
The higher their value or rating in watts, the more
electrical power they are likely to consume.
The quantity symbol for power is P and is the product of
voltage multiplied by the current with the unit of
measurement being the Watt (W).
Prefixes are used to denote the various multiples or
sub-multiples of a watt, such as: milliwatts (mW = 103
W) or kilowatts (kW = 103W).
E.
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POWER DISSIPATION
The definition of power dissipation is the process by
which an electronic or electrical device produces heat
(energy loss or waste) as an undesirable derivative of its
primary action.
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