Question

What do you mean by power rating of an electrical appliance?
How do you use it to calculate?
a) the resistance of the appliance, and
b) the safe limit of current in it, while in use?

Answer 1

Hint: An electrical appliance's rating specifies the voltage at which it is designed to operate as well as the current consumption at that voltage. The appliance's rating is determined by the amount of energy it consumes. Watts are the product of volts and amperes and are measured in watts.

Complete step-by-step solution:
The quantity of energy moved or transformed per unit time is referred to as power in physics. The watt, which is equal to one joule per second in the International System of Units, is the unit of power. Power is also referred to as activity in ancient writings. A scalar quantity is power. The product of the torque generated by a motor and the angular velocity of its output shaft is the motor's output power. The product of the traction force on the wheels and the vehicle's velocity is the power required to move a ground vehicle.
The power rating of an electrical equipment, such as an electric lamp or a geyser, is made up of two numbers: power (P) and voltage (V). Consider the following scenario: When an electric bulb is classified as 50W-220V, it signifies that it uses 50 W of electricity when powered by a 220 V source. Every electrical device has a power rating that indicates how much power it requires to operate.
Watts (W) or kilowatts (kW) are commonly used (1000W = 1kW). Of course, the quantity of power it consumes is determined by the length of time it is turned on, which is measured in kilowatt-hours (kWh).
a) the resistance of the appliance, and
We know that
P = VI
V = IR
Hence $P = \dfrac{{{V^2}}}{R}$
Which means $ \Rightarrow R = \dfrac{{{V^2}}}{P}$
b) Safe limit of current
we know that P = VI
$ \Rightarrow I = \dfrac{P}{V}$

Note:The combination of forces and movement in mechanical systems is known as power. Power is defined as the product of a force on an object and the velocity of the object, or the product of a torque on a shaft and the angular velocity of the shaft. The time derivative of work is another term for mechanical power.