What is Power?
What is Energy?
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Power is defined as the time rate at
which energy is produced or consumed,
depending on whether the element is
a source of power or a consumer of power,
repectively. It is usually expressed
in units of watts.
Power from
Voltage and Current
Engineers design electrical systems
to control electrical energy. The energy
is exchanged between parts of a circuit,
and the rate of energy flow, the power,
must be calculated. Now, we will see
how the knowledge of voltage and current
in an electric circuit allows computation
of energy flow throughout the circuit.
Let’s restate the definitions
of voltage and current and see how their
definitions relate to power flow.
• Current
is the rate of charge flow and voltage
is the energy exchange per
charge.
• Power
is defined as the time rate at which
energy is produced or
consumed;therefore
power is by definition the product of
voltage and current.
• Whether electrical
or mechanical, power pertains to the
rate at which work
is
being done, therefore
where p
= power in watts (W),
W
work in joules (J),
and t
= time in seconds (s).
When a charge dq
is moved from a
to b,
the energy given by an electric circuit
is
When continuous charge flow, a current,
is involved, the power p
is
Accordingly, more useful formula for
finding the power is
where
v = voltage drop in volts
(V),
and i
= current in amperes (A).
If we know the voltage across a circuit
component and the current through
that element, we can determine the
power into or out of that component
by multiplying voltage and current
(Watts = Volts x Amperes).
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