Enter the change in work and change in time of an object or system to calculate the total power of that system.

Power Formula

The following formulas are used to calculate power.

P (Power) = dW/dt, 
  • where W is work
  • and t is time.

To calculate Power, divide the change in work by the change in time.

Power (P) = (W2-W1)/(T2-T1)

Power (P) = (W2-W1)/(T2-T1)

  • where W1 is the initial work
  • W2 is the final work
  • T2 – T1 is the total time passed

Power can also be described as the rate of transferring heat, which is synonymous with work. The international standard unit for power is joules per second (J/s). Unlike velocity, force, and acceleration, Power is a scalar quantity and has no direction.

In terms of electricity, the output power of an electric motor is the product of the torque and the velocity, or in terms of light, it’s measured in watts.

How to calculate power

We will now take a look at an example of how to calculate power. For this example, we will be looking at an electric motor.

  1. First, we need to set up our experiment. We hook up the electric motor to a gauge that measures work overtime.
  2. Next, we run the motor for a certain amount of time. Let’s say we run it for 10 seconds and the change in work is 10 J.
  3. Finally, enter that information into the equation above. P= 10J/10s = 1W.
  4. Analyze and adjust your results.

FAQ

What is the difference between power and energy?

Energy is the total amount of work done, while power is the rate at which work is done over time. Energy is measured in joules, while power is measured in joules per second (J/s), also known as watts.

Can power be negative?

Yes, power can be negative. This typically indicates that a system is losing energy. For example, when applying brakes in a car, the kinetic energy is being converted into heat, thus the power associated with this process is considered negative.

How is power related to torque and velocity in electric motors?

In electric motors, power is the product of torque and angular velocity. Torque measures how much force is being applied to rotate an object, while velocity measures how fast the object is rotating. Thus, the power output of an electric motor can be increased by either increasing its torque or its rotational speed.