Current electricity practice · Medium

A capacitor is charged by a cell of emf $E$ and the charging battery is then removed. If an identical capacitor is now inserted in the circuit in parallel with the previous capacitor, the potential difference across the new capacitor is

A $10 \mathrm{~V}$ battery of negligible internal resistance is charged by a $200 \mathrm{~V}$ d.c. supply. If the resistance in the charging circuit is $38 \Omega$, what is the value of charging current ?

The current in a wire varies with time according to the relation $i=4+2 t^2$. How many coulomb of charge pass a cross-section of wire in time interval $t=5$ s to $t=10 s$ ?

The current of 1.6 A is flowing in a conductor. The number of electrons flowing per second through the conductor is

Two bulbs marked $\mathrm{200}\,\,\mathrm{V - }\,\,\mathrm{100}\,\,\mathrm{W}$ and $\mathrm{200}\,\,\mathrm{V}\,\mathrm{ - }\,\mathrm{200}\,\,\mathrm{W}$ are joined in series and connected to a power supply of $\mathrm{200}\,\,\mathrm{V}$. The total power consumed by the two will be near to

We are given $n$ resistors, each of resistance $r$ they are first combined to get maximum possible resistance then to get minimum possible resistance then ratio between maximum and minimum resistance is

A student measures the terminal potential difference $\left( V \right)$ of a cell (of $emf\mathrm{ }E$ and internal resistance $r$) as a function of the current $\left( I \right)$ flowing through it. The slope, and intercept, of the graph between $V$ and $I$, then, respectively, equal

When a 40 watt lamp is connected in series with a 100 watt lamp across a 210 volt supply, which one glows brighter?

The resistance of a wire is $'R'$ ohm. If it is melted and stretched to $'n'$ times its original length, its new resistance will be

The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated $\mathrm{100 W}$ and $\mathrm{200 V}$ is connected across $\mathrm{200 V}$ power supply. If the voltage drops by $\mathrm{10}\,\,\mathrm{\% }$, then the power of the lamp will be

Electrical resistance of a piece of a material sharply decreases on increasing the temperature of the piece. The material of the piece is a :

1 ampere current is equivalent to

The Earth's surface has a negative surface charge density of $\frac{135 \times 10^{-9}}{\pi(6.4)^2} \mathrm{C} / \mathrm{m}^2$. The potential difference of $400 \mathrm{kV}$ between the top of the atmosphere and the surface, results (due to low conductivity of the lower atmosphere) in a current of only $1800 \mathrm{~A}$ over the entire globe. If there is no mechanism of sustaining atmospheric electric field, how much time (in sec) would be required to neutralize the Earth's surface?$\left(\right.$ Radius of earth $\left.=6.4 \times 10^6 \mathrm{~m}\right)$

The current in a conductor varies with time $t$ as $I = 2t + \,\,3{t^2}$ where $I$ is in ampere and $t$ in seconds. Electric charge flowing through a section of the conductor during $t = 2\,\,\sec$ to $t = 3\,\,\sec$ is

A thermocouple is made from two metals, Antimony and Bismuth. If one junction of the couple is kept hot and the other is kept cold, then, an electric current will

A parallel combination of three resistors takes a current of $7.5 \mathrm{~A}$ from a $30 \mathrm{~V}$ supply. If the two resistors are $10 \Omega$ and $12 \Omega$, find the third one.

Kirchhoff’s first law $i.e.\,\,\sum i = 0$ at a junction is based on the law of conservation of

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

The mass of ions deposited during a given interval of time in the process of electrolysis depends on

The lengths of the three wires of copper are in the ratio of $1: 4: 8$ and their masses are in the ratio of $5: 3: 1$. The ratio of their electrical resistance is

The electric current passing through a metallic wire produces heat because of

The tungsten filaments of two electric bulbs are of the same length. If one of them gives $25 {~W}$ power and the other $60 {~W}$ power. Then

In which of the following cases ohm's law is not valid?

In the above question if potential difference is applied, the drift velocity at temperature $T$ is

Show that one ampere is equivalent to a flow of $6.25 \times 10^{18}$ elementary charges per second.

Wires ${P}$ and ${Q}$ are having same resistance at room temperature. When heated, resistance of ' $P$ ' increases, and that of ' $Q$ ' decreases, we conclude that

Which of the following statements are incorrect?

I. The order of magnitude of current flowing in household appliances is one ampere.

II. The order of magnitude of current in lightening is about one ampere.

III. The order of magnitude of current in nerves in human body is one ampere.

When the temperature of a metallic resistor is increased, the product of its resistivity and conductivity

The current density of a solid cylindrical wire of radius ${R}$, as a function of radial distance ${r}$ is given by $J(r)=J_0\left(1-\frac{r}{R}\right)$. The total current in the radial region ${r}=0$ to $r=\frac{R}{4}$ will be:

Assertion: Potentiometer measures the correct value of emf of a cell.
Reason: No current flows through the cell being balanced at the null point of potentiometer.