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The efficiency of a Carnot engine depends upon:
A galvanometer of resistance G is shunted by a resistance S ohm. To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is
The net resistance of a voltmeter should be large to ensure that:
If a charged particle (charge q) is moving in a circle of radius R at a uniform speed v, then the value of its associated magnetic moment μ will be:
A wheel with 20 metallic spokes, each 1 m long, is rotated with a speed of 120 rpm in a plane perpendicular to a magnetic field of 0.4 G. The induced emf between the axle and rim of the wheel will be: (1 G = 10⁻⁴ T)
Two spheres A and B of masses $m_1$ and $m_2$ respectively collide. A is at rest initially and B is moving with velocity $v$ along x-axis. After collision B has a velocity $\frac{v}{2}$ in a direction perpendicular to the original direction. The mass A moves after collision in the direction:
A 250 turn rectangular coil of length $2.1 \text{ cm}$ and width $1.25 \text{ cm}$ carries a current of $85 \, \mu\text{A}$ and subjected to the magnetic field of strength $0.85 \text{ T}$. Work done for rotating the coil by $180^{\circ}$ against the torque is:
Ionized hydrogen atoms and $\alpha$-particles with the same momenta enter perpendicular to a constant magnetic field, $B$. The ratio of their path radii $r_H : r_\alpha$ will be:
An LED is constructed from a p-n junction diode using GaAsP. The energy gap is $1.9 \text{ eV}$. The wavelength of the light emitted will be equal to:
A moving coil galvanometer has a resistance of $50\ \Omega$ and gives full scale deflection for $10\ \text{mA}$. How could it be converted into an ammeter with a full scale deflection for $1\ \text{A}$?
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:
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)
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: