Current Electricity

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.

The number of electrons flowing per second in the filament of a $110 \mathrm{~W}$ bulb operating at $220 \mathrm{~V}$ is : (Given $\mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$)

If an ammeter is to be used in place of a voltmeter, then we must connect with the ammeter a

The thermo $e.m.f.$ of a thermo -couple is $25$ $\mu V/{}^ \circ C$ at room temperature. A galvanometer of $40$ $ohm$ resistance, capable of detecting current as low as ${10^{ - 5}}\,A,$ is connected with the thermo couple. The smallest temperature difference that can be detected by this system is

An ammeter reads upto $1$ ampere. Its internal resistance is $0.81$ $ohm$. To increase the range to $10$ $A$ the value of the required shunt is

A moving coil galvanometer has $150$ equal divisions. Its current sensitivity is $10$- divisions per milliampere and voltage sensitivity is $2$ divisions per millivolt. In order that each division reads $1$ volt, the resistance in $ohms$ needed to be connected in series with the coil will be -

Two voltmeters, one of copper and another of silver, are joined in parallel. When a total charge $q$ flows through the voltmeters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are ${Z_1}$ and ${Z_2}$ respectively the charge which flows through the silver voltmeter is

This questions has Statement - ${\rm I}$ and Statement - ${\rm I}$${\rm I}$. Of the four choices given after the Statements, choose the one that best describes into two Statements. Statement - ${\rm I}$ : Higher the range, greater is the resistance of ammeter. Statement - ${\rm I}$${\rm I}$ : To increase the range of ammeter, additional shunt needs to be used across it.

A 50 $\Omega$ resistance is connected to a battery of 5 V. A galvanometer of resistance 100 $\Omega$ is to be used as an ammeter to measure current through the resistance, for this a resistance r_s is connected to the galvanometer. Which of the following connections should be employed if the measured current is within 1% of thecurrent without the ammeter in the circuit ?

A galvanometer having a coil resistance of $100\,\Omega$ gives a full scale deflection, when a currect of $1$ $mA$ is passed through it. The value of the resistance, which can convert this galvanometer into ammeter giving a full scale deflection for a current of $10$ $A,$ is :