Current electricity practice · Medium

The accurate measurement of emf can be obtained using

An ammeter reads $\mathrm{0}\mathrm{.90}\,\,\mathrm{A}$ when connected in series with a silver voltmeter that deposits $\mathrm{2}\mathrm{.60 }\,\mathrm{g}$ of silver in $\mathrm{40}\,\,\mathrm{min}$. By what percentage is the ammeter reading is correct? Atomic weight of silver $\mathrm{ = 108}\,\,\,\mathrm{and}\,\,\mathrm{1}\,\,\mathrm{F}\,\mathrm{ = }\,\mathrm{96500}\,\,\mathrm{C}$ ?

Assertion: EMF of battery decreases with time.
Reason: Internal resistance increases with time.

A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it

Find the true statements

A resistor ${R_1}$ dissipates power $P$ when connected to a certain generator. If the resistor ${R_2}$ is put in series with ${R_1}$, the power dissipated by ${R_1}$

A constant voltage is applied between two ends of a metallic wire. If the wire is replaced by another wire of same material, half the length and doubled the radius, the rate of heat developed in the wire will be:

A lead acid accumulatory (storage battery) is connected to a battery charge for over night charging. Which of the following observations will indicate that the battery was partly charged during the next morning

To get the maximum current from a parallel combination of $n$ identical cells each of internal resistance $r$ and external resistance $R$, when

In water voltmeter, the electrolysis of …… takes place

Which of the following has a negative temperature coefficient

Assertion (A)In a meter bridge experiment, null point for an unknown resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at the same ${p}$ as before by decreasing the value of the standard resistance.

Reason (R) Resistance of metal increases with increase in temperature.

A student in a town in India, where the price per
unit (1 unit = 1 kW-h) of electricity is `5.00,
purchases a 1 kVA UPS (uninterrupted power
supply) battery. A day before the exam, 10
friends arrive to the student’s home with their
laptops and all connect their laptops to the UPS.
Assume that each laptop has a constant power
requirement of 90 W. Consider the following
statements

I. All the 10 laptops can be powered by the
UPS if connected directly.

II. All the 10 laptops can be powered if
connected using an extension box with a
3A fuse.

III. If all the 10 friends use the laptop for 5 hours,
then the cost of the consumed electricity is
about `22.50.

Select the correct option with the true
statements.

By mistake a voltmeter is connected in series and an ammeter is connected in parallel with a resistance in an electrical circuit. What will happen to the instrument?

A conductor wire having ${10^{29}}$ free $\mathrm{electrons}/{\mathrm{m}^3}$ carries a current of $\mathrm{20}\,\,\mathrm{A}\,$. If the cross-section of the wire is $1\,\,\mathrm{m}{\mathrm{m}^2}$, then the drift velocity of electrons will be

Material that is widely used to make wire bound standard resistors is

Masses of the three wires of same material are in the ratio of $1:2:3$ and their lengths in the ratio of $3:2:1$. Electrical resistance of these wires will be in the ratio of

Assertion: When Wheatstone bridge is balanced, the current through the cell depends on the resistance of galvanometer.
Reason: In the balanced condition, current through the galvanometer is very high.

The length of a conductor is doubled and its radius is halved, its specific resistance is

For a thermocouple, the inversion temperature is $600\,^\circ C$  and the neutral temperature is $320\,^\circ C$. Find the temperature of the cold junction?

Twelve wires of equal resistance $R$ are connected to form a cube. The effective resistance between two opposite diagonal ends will be

Thermoelectric constant of a thermocouple are $\alpha$ and $\beta .$. Thermoelectric power at inversion temperature is

Assertion (A) : If potential difference across two points is zero, current between these two points should be zero.

Reason (R): Current passing from a resistor $I=\frac{V}{R}$

A certain electrical conductor has a square cross-section, $\mathrm{2}\mathrm{.0}\,\,\mathrm{mm}$ on side, and is $\mathrm{12 m}$ long. The resistance between its ends is $0.072\,\,\mathrm{\Omega }$. The resistivity of its material is equal to

A battery of emf $\mathrm{2}\,\,\mathrm{V}$ and internal resistance $0.1\,\,\Omega$ is being charged by a current of $\mathrm{5}\,\,\mathrm{A}$. the potential difference between the terminals of the battery is

In a Wheatstone bridge, $P = 90\,\,\mathrm{\Omega },\,\,Q = 110\,\,\mathrm{\Omega },\,\,R = 40\,\,\mathrm{\Omega }\,\,\mathrm{and}\,\,S = 60\,\,\mathrm{\Omega }$ and a cell of $\mathrm{4}\,\,\mathrm{V}$ emf. Then the potential difference between the diagonal along which a galvanometer is connected is

A wire is cut into 4 pieces, which are put together by sides to obtain one conductor. If the original resistance of wire was $R$, the resistance of the buridle will be

$Watt - hour$ meter measures