A heating element is a device that converts electrical energy into heat. It is commonly used in appliances like stoves, toasters, and water heaters to generate the necessary warmth.
A student boils water in an electric kettle for 20 minutes. Using the same mains supply he wants to reduce the boiling time of water. To do so should he increase or decrease the length of the heating element? Justify your answer.
Share
To reduce the boiling time using the same mains supply, the rate of heat production should be large. We know that
P = V2/R
Since V is constant, R should be decreased. Since R is directly proportional to l so length should be decreased.
The time it takes to boil water in an electric kettle is influenced by several factors, including the power of the heating element, the initial temperature of the water, and the efficiency of the kettle. Let’s focus on the impact of the length of the heating element.
The power (P) of the heating element is given by the formula:
P = V2/R
where:
P is power,
V is voltage, and
R is resistance.
The heating effect, which determines how quickly the water heats up, is given by the formula:
H = I2.R.t
where:
H is the heating effect,
I is current,
R is resistance, and
t is time.
The resistance (R) of the heating element is directly proportional to its length (L). Therefore, if the student wants to reduce the boiling time, he should aim to increase the power of the heating element, and subsequently, the heating effect.
To achieve this without changing the voltage or current (which are typically fixed by the mains supply), the student should decrease the resistance of the heating element. Since resistance is directly proportional to the length of the heating element, reducing the length of the heating element will decrease its resistance.
In conclusion, to reduce the boiling time of water, the student should decrease the length of the heating element.