Water boils in an electric kettle in 20 minut | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(C) The power consumed by the heating element is given by $P = V^2/R$,where $V$ is the supply voltage and $R$ is the resistance.Since $R = \rho \ell/A

Vedclass · Accepted Answer

decreased,$3/4$

Vedclass · Answer

(C) The power consumed by the heating element is given by $P = V^2/R$,where $V$ is the supply voltage and $R$ is the resistance.Since $R = ho \ell/A$,where $ho$ is resistivity,$\ell$ is length,and $A$ is the cross-sectional area,we have $P \propto 1/\ell$.The heat required to boil the water is $H = P 	imes t$. Since $H$ is constant,$P_1 t_1 = P_2 t_2$.Therefore,$P_1/P_2 = t_2/t_1 = 15/20 = 3/4$.Since $P \propto 1/\ell$,we have $P_1/P_2 = \ell_2/\ell_1$.Thus,$\ell_2/\ell_1 = 3/4$.Since the new length $\ell_2$ is $3/4$ of the initial length $\ell_1$,the length must be decreased to $3/4$ of its initial length.

Water boils in an electric kettle in $20$ minutes after being switched on. Using the same main supply,the length of the heating element should be . . . . . . to . . . . . . times of its initial length if the water is to be boiled in $15$ minutes.

Similar Questions

Power generated across a uniform wire connected across a supply is $H$. If the wire is cut into $n$ equal parts and all the parts are connected in parallel across the same supply,the total power generated in the wire is

$A$ bulb of $100 \text{ W}$ rating is connected with $220 \text{ V}$ supply. The resistance of the bulb is . . . . . . .

The current flowing through a lamp marked as $50\, W$ and $250\, V$ is ............. $amp$.

An electric bulb marked $40\, W$ and $200\, V$,is used in a circuit of supply voltage $100\, V$. Now its power is (in $, W$)

Two electric bulbs have resistances in the ratio $1 : 2$. If they are connected in parallel to a constant voltage source,the ratio of power dissipated in them will be:

Vedclass Test Series

Exam Paper Generator

Online Exam Module