Power electric circuit uses characteristics advantages disadvantages power in electrical circuit formulas

1. Power and Energy
Dr. Asad Abbas
University of Central Punjab

2. Power (Watts W)
 Power (P) is a certain amount of energy (W) used
in certain length of time (t).
P=W/t
 W is energy in joules (J).
 If 50 J of energy are used in 2s,
 The power is 50J/2=25W

3. Energy (joule W)
 Energy is the ability to do work, and power is the rate at
which energy is used.
 Energy in joules divided by time in seconds gives power in
watts.
 Thus, the number of joules used in one second is always
equal to the number of watts.
 If 75 J are used in 1 s, the power is P=W/t= 75J/1s=75W

4. Watts W
 A Watt is the unit of electrical power equal to one ampere
under the pressure of one volt. One Watt is a small amount of
power. Some devices require only a few Watts to operate, and
other devices require larger amounts.
W=Pt
 As with small current and voltage values, metric prefixes are
used to designate small amount of power.
 Thus milliwatts (mW) and microwatts (uW) are commonly found
in some applications

5. Horsepower (hp)
 Another larger power unit in common use is the
horsepower.
 Large electric motors are commonly rated in
horsepower (hp).
1 hp= 746 W

6. Power in Electric Circuit
 Determine power when you know I and R.
 Determine power when you know V and I.
 Determine power when you know V and R.

7. Power in Electric Circuit
 When there is current through resistance, the collisions of
the electrons produce heat as a result of the conversion of
electrical energy.
 The amount of power dissipated in an electric circuit is
dependent on the amount of resistance and on the
amount of current.
P=𝐼2R

8. Power in Electric Circuit
P=(I*I)R
P=I(IR)
P=VI
Where V is Joules per coulomb and I is coulomb per sec.
P=
𝑗𝑜𝑢𝑙𝑒𝑠
𝑐𝑜𝑢𝑙𝑜𝑚𝑏
𝑐𝑜𝑢𝑙𝑜𝑚𝑏
𝑠𝑒𝑐
= (
𝑗𝑜𝑢𝑙𝑒𝑠
𝑠𝑒𝑐
)=watts
 The relationships between power and current, voltage and resistance
expression the preceding formulas are known as Watts’s law.

9.  P=VI=V(V/R)
 P=𝑉2/𝑅