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The magnitude and direction of the current in the following circuit is:
Net EMF $= 10 - 5 = 5$ V (cells oppose), total $R = 2+1+7 = 10\ \Omega$, current $= 0.5$ A driven by the 10 V cell, so from $A$ to $B$ through $E$.
In hydrogen spectrum, the shortest wavelength in the Balmer series is $\lambda$. The shortest wavelength in the Bracket series is:
Series limit: $1/\lambda_{\min} = R/n^2$. Balmer ($n=2$): $1/\lambda = R/4$. Bracket ($n=4$): $1/\lambda' = R/16$. So $\lambda' = 4\lambda$.
An electric dipole is placed at an angle of $30^\circ$ with an electric field of intensity $2\times 10^5\ \text{N C}^{-1}$. It experiences a torque equal to $4\ \text{N m}$. Calculate the magnitude of charge on the dipole, if the dipole length is $2\ \text{cm}$.
$\tau = qLE\sin\theta\Rightarrow q = \dfrac{4}{0.02 \times 2\times 10^5 \times 0.5} = 2\times 10^{-3}\ \text{C} = 2\ \text{mC}$.
The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to $\left(\dfrac{1}{16}\right)^{th}$ of its initial value?
$1/16 = (1/2)^4$, so 4 half-lives $= 4\times 20 = 80$ min.
The venturi-meter works on:
A venturi-meter measures flow rate via pressure difference, derived from Bernoulli's equation.
An ac source is connected to a capacitor $C$. Due to decrease in its operating frequency:
$X_C = 1/(\omega C)$ increases as $\omega$ decreases, so current $I = V/X_C$ (and displacement current) decreases.
A football player is moving southward and suddenly turns eastward with the same speed to avoid an opponent. The force that acts on the player while turning is:
$\Delta\vec{v} = \vec{v}_f - \vec{v}_i$ points north-east (east minus south $=$ east + north). Force is along $\Delta\vec{v}$, i.e., north-east.
A full wave rectifier circuit consists of two p-n junction diodes, a centre-tapped transformer, capacitor and a load resistance. Which of these components remove the ac ripple from the rectified output?
A shunt capacitor (filter) smooths the pulsating dc by charging on rising and discharging slowly on falling cycles.
The potential energy of a long spring when stretched by 2 cm is $U$. If the spring is stretched by 8 cm, potential energy stored in it will be:
$U\propto x^2$; $(8/2)^2 = 16$, so $U_2 = 16U$.
In a plane electromagnetic wave travelling in free space, the electric field component oscillates sinusoidally at a frequency of $2.0\times 10^{10}\ \text{Hz}$ and amplitude $48\ \text{V m}^{-1}$. Then the amplitude of oscillating magnetic field is: (Speed of light in free space $= 3\times 10^8\ \text{m s}^{-1}$)
$B_0 = E_0/c = 48/(3\times 10^8) = 1.6\times 10^{-7}\ \text{T}$.
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The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.