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A step-down transformer connected to an AC mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?
A galvanometer has 30 divisions and a sensitivity $16\ \mu\text{A/div}$. It can be converted into a voltmeter to read $3\ \text{V}$ by connecting (approximately):
For the circuit shown in the figure, the time constant is:
The resistance of an ammeter is 13 Ω and its scale is graduated for a current up to 100 A. After an additional shunt has been connected to this ammeter, it becomes possible to measure currents up to 750 A by this ammeter. The value of shunt resistance is:
A rectangular coil of length $0.12 \text{ m}$ and width $0.1 \text{ m}$ having $50$ turns of wire is suspended vertically in a uniform magnetic field of strength $0.2 \text{ Wb/m}^2$. The coil carries a current of $2 \text{ A}$. If the plane of the coil is inclined at an angle of $30^\circ$ with the direction of the field, the torque required to keep the coil in stable equilibrium will be:
The current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is:
In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential $V$ and then made to describe semi-circular paths of radius $R$ using a magnetic field $B$. If $V$ and $B$ are kept constant, the ratio of $\left(\frac{\text{Charge on the ion}}{\text{Mass of the ion}}\right)$ $\left(\frac{q}{m}\right)$ will be proportional to:
A cylindrical conductor of radius R is carrying a constant current. The plot of the magnitude of the magnetic field B with the distance d from the centre of the conductor is correctly represented by the figure:
A wire of length $L$ meters carrying a current of $I$ ampere is bent in the form of a circle. What is its magnetic moment?
The oscillation of a body on a smooth horizontal surface is represented by the equation, $X = A \cos(\omega t)$, where $X =$ displacement at time $t$, $\omega =$ frequency of oscillation. Which one of the following graphs correctly shows the variation of acceleration, $a$ with time, $t$? ($T =$ time period)
The minimum wavelength of X-rays produced by an electron accelerated through a potential difference of $V$ volts is proportional to
When a block of mass M is suspended by a long wire of length L, the length of the wire becomes (L + l). The elastic potential energy stored in the extended wire is :
The simple Bohr model is not applicable to He-4 atom because: (a) He-4 is an inert gas. (b) He-4 has neutrons in the nucleus. (c) He-4 has one more electron. (d) electrons are not subject to central forces. Choose the correct option:
A straight conductor carrying current $I$ splits into two parts as shown in the figure. The radius of the circular loop is $R$. The total magnetic field at the centre $P$ of the loop is:
A square loop ABCD carrying a current $i$ is placed near and coplanar with a long straight conductor XY carrying a current $I$. The net force on the loop will be:
A vertical spring with a force constant $k$ is fixed on a table. A ball of mass $m$ at a height $h$ above the free upper end of the spring falls vertically on the spring so that the spring is compressed by a distance $d$. The net work done in the process is:
A current loop in a magnetic field:
In an ideal transformer, the turns ratio is $N_p/N_s = 1/2$. The ratio $V_s:V_p$ is equal to (the symbols carry their usual meaning):
Two toroids 1 and 2 have total no. of turns 200 and 100 respectively with average radii 40 cm and 20 cm respectively. If they carry the same current i, what will be the ratio of the magnetic fields along the two loops?
A uniform conducting wire of length $12a$ and resistance $R$ is wound up as a current-carrying coil in the shape of: (i) an equilateral triangle of side $a$ (ii) a square of side $a$ The magnetic dipole moments of the coil in each case respectively are: