List of top Physics Questions

In the figure shown below, the charge on the left plate of the $10 \; \mu F$ capacitor is $-30 \; \mu C$ . The charge on the right plate of the $6 \; \mu F$ capacitor is :

In the circuit shown, find $C$ if the effective capacitance of the whole circuit is to be $0.5 \mu F$. All values in the circuit are in $\mu F$.

In the figure shown, after the switch $'S'$ is turned from position $'A'$ to position $'B'$, the energy dissipated in the circuit in terms of capacitance $'C'$ and total charge $'Q'$ is:

A plane electromagnetic wave of frequency $50\, MHz$ travels in free space along the positive $x$-direction. At a particular point in space and time, $\vec{E} = 6.3 \hat{j} V/m$ . The corresponding magnetic field $\vec{B}$ , at that point will be:

An ideal battery of $4\, V$ and resistance $R$ are connected in series in the primary circuit of a potentiometer of length $1\, m$ and resistance $5\Omega$. The value of $R$, to give a potential difference of $5 \,mV$ across $10\, cm$ of potentiometer wire, is :

Drift speed of electrons, when $1.5\, A$ of current flows in a copper wire of cross section $5\, mm^2$, is $v$. If the electron density in copper is $9 \times 10^{28} /m^3$ the value of $v$ in mm/s is close to (Take charge of electron to be = $1.6 \times 10^{-19}C$)

In a meter bridge, the wire of length $1\, m$ has a non-uniform cross-section such that, the variation $\frac{dR}{dl}$ of its resistance $R$ with length $l$ is $\frac{dR}{dl} \propto \frac{1}{\sqrt{l}}$. Two equal resistances are connected as shown in the figure. The galvanometer has zero deflection when the jockey is at point $P$. What is the length $AP$ ?

In the experimental set up of metre bridge shown in the figure, the null point is obtained at a distance of $40\, cm$ from $A$. If a $10 \Omega$ resistor is connected in series with $R_1$, the null point shifts by $10\, cm$. The resistance that should be connected in parallel with $(R_1 + 10)\Omega$ such that the null point shifts back to its initial position is :

In the given circuit, an ideal voltmeter connected across the $10\, \Omega$ resistance reads $2V$. The internal resistance $r$, of each cell is :

In the given circuit diagram, the currents, $I_1 = 0.3\,A, I_4 = 0.8\, A$ and $I_5 = 0.4\, A$, are flowing as shown. The currents $I_2,I_3$ and $I_6$,respectively, are :

In the given circuit the cells have zero internal resistance. The currents (in Amperes) passing through resistance $R_1$, and $R_2$ respectively, are:

The Wheatstone bridge shown in Fig. here, gets balanced when the carbon resistor used as $R_1$ has the colour code ( Orange, Red, Brown). The resistors $R_2$ and $R_4$ are $80\Omega $ and $40 \Omega $ respectively. Assuming that the colour code for the carbon resistors gives their accurate values, the colour code for the carbon resistor, used as $R_3$, would be :

When the switch $S$, in the circuit shown, is closed, then the value of current $i$ will be :

The resistance of the meter bridge $AB$ is given figure is $4\Omega$ . With a cell of emf $\varepsilon = 0.5 \;V $ and rheostat resistance $R_h = 2 \; \Omega$ the null point is obtained at some point $J$. When the cell is replaced by another one of emf $\varepsilon = \varepsilon_2$ the same null point $J$ is found for $R_h = 6 \; \Omega$. The emf $\varepsilon_2$ is;

In the circuit shown, a four-wire potentiometer is made of a $400\, cm$ long wire, which extends between $A$ and $B$. The resistance per unit length of the potentiometer wire is $r = 0.01 $ $\Omega/cm$. If an ideal voltmeter is connected as shown with jockey $J$ at $50\, cm$ from end $A$, the expected reading of the voltmeter will be :

A cell of internal resistance r drives current through an external resistance $R$. The power delivered by the cell to the external resistance will be maximum when

A $2\, W$ carbon resistor is color coded with green, black, red and brown respectively. The maximum current which can be passed through this resistor is :

An electric dipole is formed by two equal and opposite charges $q$ with separation $d$. The charges have same mass $m$. It is kept in a uniform electric field $E$. If it is slightly rotated from its equilibrium orientation, then its angular frequency $\omega$ is :

Consider the $LR$ circuit shown in the figure. If the switch $S$ is closed at $t = 0$ then the amount of charge that passes through the battery between $t = 0$ and $t = \frac{L}{R}$ is:

At some location on earth the horizontal component of earth's magnetic field is $18 \times 10^{-6}$ T. At this location, magnetic needle of length $0.12\, m$ and pole strength $1.8\, Am$ is suspended from its mid-point using a thread, it makes $45^{\circ}$ angle with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is :

A common emitter amplifier circuit, built using an npn transistor, is shown in the figure. Its dc current gain is $250, \,R_C = 1k\Omega$ and $V_{CC} = 10 V$. What is the minimum base current for $V_{CE}$ to reach saturation ?

Due to Doppler?? effect the shift in wavelength observed is 0.1 ? for a star producing wavelength 6000 ?. Velocity of recession of the star will be

A light ray of wavelength 600 nm in incident on young's double slit experiment. Distance between silts is 2 mm and \( 5^{th}\) fringe is at a distance of 3 mm from central maxims, find the distance between slits and screen:

A concave mirror has radius of curvature of $40\, cm$. It is at the bottom of a glass that has water filled up to $5\, cm$ (see figure). If a small particle is floating on the surface of water, its image as seen, from directly above the glass, is at a distance d from the surface of water. The value of d is close to : (Refractive index of water $= 1.33$)

A convex lens (of focal length $20\, cm$) and a concave mirror, having their principal axes along the same lines, are kept $80 \,cm$ apart from each other. The concave mirror is to the right of the convex lens. When an object is kept at a distance of $30\, cm$ to the left of the convex lens, its image remains at the same position even if the concave mirror is removed. The maximum distance of the object for which this concave mirror, by itself would produce a virtual image would be :