The figure shows an experimental plot for discharging of a capacitor in an R–C circuit.
Question: The figure shows an experimental plot for discharging of a capacitor in an $\mathrm{R}-\mathrm{C}$ circuit. The time constant $\tau$ of this circuit lies between:-$100 \mathrm{sec}$ and $150 \mathrm{sec}$$150 \mathrm{sec}$ and $200 \mathrm{sec}$0 and $50 \mathrm{sec}$$50 \mathrm{sec}$ and $100 \mathrm{sec}$Correct Option: 1 Solution:...
Read More →Combination of two identical capacitors, a resistor R and a dc voltage source of voltage 6V is used in an experiment on (C–R) circuit.
Question: Combination of two identical capacitors, a resistor $\mathrm{R}$ and a dc voltage source of voltage 6V is used in an experiment on $(\mathrm{C}-\mathrm{R})$ circuit. It is found that for a parallel combination of the capacitor the time in which the voltage of the fully charged combination reduces to half its original voltage is 10 second. For series combination the time needed for reducing the voltage of the fully charged series combination by half is :-20 second10 second5 second2.5 se...
Read More →Dimensions of
Question: Dimensions of $\frac{1}{\mu_{0} \in_{0}}$, where symbols have their usual meaning, are-$\left[\mathrm{L}^{-1} \mathrm{~T}\right]$$\left[\mathrm{L}^{2} \mathrm{~T}^{2}\right]$$\left[\mathrm{L}^{2} \mathrm{~T}^{-2}\right]$$\left[\mathrm{LT}^{-1}\right]$Correct Option: , 3 Solution:...
Read More →A resistor 'R' and 2µF capacitor in series is connected through a switch to 200 V direct supply.
Question: A resistor 'R' and $2 \mu \mathrm{F}$ capacitor in series is connected through a switch to $200 \mathrm{~V}$ direct supply. Across the capacitor is a neon bulb that lights up at $120 \mathrm{~V}$. Calculate the value of $\mathrm{R}$ to make the bulb light up $5 \mathrm{~s}$ after the switch has been closed. $\left(\log _{10} 2.5=0.4\right)$$2.7 \times 10^{6} \Omega$$3.3 \times 10^{7} \Omega$$1.3 \times 10^{4} \Omega$$1.7 \times 10^{5} \Omega$Correct Option: 1 Solution:...
Read More →Two identical charged spheres are suspended by strings of equal lengths.
Question: Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of $30^{\circ}$ with each other. When suspended in a liquid of density $0.8 \mathrm{~g} \mathrm{~cm}^{-3}$, the angle remains the same. If density of the material of the sphere is $1.6 \mathrm{~g} \mathrm{~cm}^{-3}$, the dielectric constant of the liquid is :1432Correct Option: , 4 Solution:...
Read More →Let C be the capacitance of a capacitor discharging through a resistor R.
Question: Let $\mathrm{C}$ be the capacitance of a capacitor discharging through a resistor $R$. Suppose $\mathrm{t}_{1}$ is the time taken for the energy stored in the capacitor to reduce to half its initial value and $t_{2}$ is the time taken for the charge to reduce to one-fourth its initial value. Then the ratio $t_{1} / t_{2}$ will be :211/21/4Correct Option: , 3 Solution:...
Read More →An external pressure
Question: An external pressure $P$ is applied on a cube at $0^{\circ} \mathrm{C}$ so that it is equally compressed from all sides. $K$ is the bulk modulus of the material of the cube and $\alpha$ is its coefficient of linear expansion. Suppose we want to bring the cube to its original size by heating. The temperature should be raised by : $\frac{3 \alpha}{P K}$$3 P K \alpha$$\frac{\mathrm{P}}{3 \alpha K}$$\frac{\mathrm{P}}{\alpha \mathrm{K}}$Correct Option: , 3 Solution:...
Read More →Solve the following
Question: If $\mathrm{a}, \mathrm{b}, \mathrm{c}, \mathrm{d}$ are inputs to a gate and $\mathrm{x}$ is its output, then as per the following time graph, the gate is NANDNOTANDORCorrect Option: , 4 Solution: Output of OR gate is 0 when all inputs are 0 \ output is 1 when atleast one of the input is 1 . Observing output $x$ :- It is 0 when all inputs are $0 \$ it is 1 when atleast one of the inputs is $1 .$ $\therefore$ OR gate...
Read More →For a common emitter configuration
Question: For a common emitter configuration, if $\alpha$ and $\beta$ have their usual meanings, the incorrect relationship between $\alpha$ and $\beta$ is$\alpha=\frac{\beta^{2}}{1+\beta^{2}}$$\frac{1}{\alpha}=\frac{1}{\beta}+1$$\alpha=\frac{\beta}{1-\beta}$$\alpha=\frac{\beta}{1+\beta}$Correct Option: , 4 Solution:...
Read More →The forward biased diode connection is:
Question: The forward biased diode connection is:Correct Option: , 4 Solution: If $\mathrm{n}$ side is at low potential relative to $\mathrm{P}$ side then diode is forward bias....
Read More →Solve this following
Question: A pendulume clock loses $12 \mathrm{~s}$ a day if the temperature is $40^{\circ} \mathrm{C}$ and gains $4 \mathrm{~s}$ a day if the temperature is $20^{\circ} \mathrm{C}$. The temperature at which the clock will show correct time, and the coeffecient of linear expansion $(\alpha)$ of the metal of the pendulum shaft are respectively :- $55^{\circ} \mathrm{C} ; \alpha=1.85 \times 10^{-2} /{ }^{\circ} \mathrm{C}$$25^{\circ} \mathrm{C} ; \alpha=1.85 \times 10^{-5} /{ }^{\circ} \mathrm{C}$$...
Read More →The I-V characteristic of an LED is
Question: The I-V characteristic of an LED isCorrect Option: , 4 Solution: I $\alpha \frac{1}{\lambda}$ more $\lambda$, less intensity and less energy....
Read More →A pendulum made of a uniform wire of cross sectional area A has time period T.
Question: A pendulum made of a uniform wire of cross sectional area A has time period T. When an additional mass $\mathrm{M}$ is added to its bob, the time period changes to $\mathrm{T}_{\mathrm{M}}$. If the Young's modulus of the material expansion $(\alpha)$ of the metal of the pendulum shaft are respectively :- $55^{\circ} \mathrm{C} ; \alpha=1.85 \times 10^{-2} /{ }^{\circ} \mathrm{C}$$25^{\circ} \mathrm{C} ; \alpha=1.85 \times 10^{-5} /{ }^{\circ} \mathrm{C}$$60^{\circ} \mathrm{C} ; \alpha=...
Read More →Two batteries with e.m.f 12 V and 13 V are connected in parallel across a load resistor of
Question: Two batteries with e.m.f $12 \mathrm{~V}$ and $13 \mathrm{~V}$ are connected in parallel across a load resistor of $10 \Omega$. The internal resistances of the two batteries are $1 \Omega$ and $2 \Omega$ respectively. The voltage across the load lies between.$11.5 \mathrm{~V}$ and 11.6 V$11.4 \mathrm{~V}$ and $11.5 \mathrm{~V}$$11.7 \mathrm{~V}$ and $11.8 \mathrm{~V}$$11.6 \mathrm{~V}$ and $11.7 \mathrm{~V}$Correct Option: 1 Solution:...
Read More →Truth table for system of four NAND gates as shown in figure is:
Question: Truth table for system of four NAND gates as shown in figure is: Correct Option: 3, Solution: Theory based....
Read More →The pressure that has to be applied to the ends of a steel wire of length
Question: The pressure that has to be applied to the ends of a steel wire of length $10 \mathrm{~cm}$ to keep its length constant when its temperature is raised by $100^{\circ} \mathrm{C}$ is : (For steel Young's modulus is $2 \times 10^{11} \mathrm{~N} \mathrm{~m}^{-2}$ and coefficient of thermal expansion is $1.1 \times 10^{-5} \mathrm{~K}^{-1}$ ) $2.2 \times 10^{7} \mathrm{~Pa}$$2.2 \times 10^{6} \mathrm{~Pa}$$2.2 \times 10^{8} \mathrm{~Pa}$$2.2 \times 10^{9} \mathrm{~Pa}$Correct Option: , 3 ...
Read More →On interchanging the resistances, the balance point of a meter bridge shifts to the left by
Question: On interchanging the resistances, the balance point of a meter bridge shifts to the left by $10 \mathrm{~cm}$. The resistance of their series combination is $1 \mathrm{k} \Omega$. How much was the resistance on the left slot before interchanging the resistances ?$505 \mathrm{k} \Omega$$550 \mathrm{k} \Omega$$910 \mathrm{k} \Omega$$990 \mathrm{k} \Omega$Correct Option: , 2 Solution:...
Read More →The combination of gates shown below yields.
Question: The combination of gates shown below yields. XOR gateNAND gateOR gateNOT gateCorrect Option: , 3 Solution:...
Read More →In a potentiometer experiment,
Question: In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across $52 \mathrm{~cm}$ of the potentiometer wire. If the cell is shunted by a resistance of $5 \Omega$, a balance is found when the cell is connected across $40 \mathrm{~cm}$ of the wire. Find the internal resistance of the cell.$1.5 \Omega$$2 \Omega$$2.5 \Omega$$1 \Omega$Correct Option: 1 Solution:...
Read More →A copper ball of mass
Question: A copper ball of mass $100 \mathrm{gm}$ is at a temperature T. It is dropped in a copper calorimeter of mass $100 \mathrm{gm}$, filled with $170 \mathrm{gm}$ of water at room temperature. Subsequently, the temperature of the system is found to be $75^{\circ} \mathrm{C}$. $\mathrm{T}$ is given by: (Given : room temperature $=30^{\circ} \mathrm{C}$, specific heat of copper $=0.1 \mathrm{cal} / \mathrm{gm}^{\circ} \mathrm{C}$ )$1250^{\circ} \mathrm{C}$$825^{\circ} \mathrm{C}$$800^{\circ} ...
Read More →Solve this
Question: $100 \mathrm{~g}$ of water is heated from $30^{\circ} \mathrm{C}$ to $50^{\circ} \mathrm{C}$ Ignoring the slight expansion of the water, the change in its internal energy is (specific heat of water is $4184 \mathrm{~J} / \mathrm{kg} / \mathrm{K}$ ) :-$84 \mathrm{~kJ}$$2.1 \mathrm{~kJ}$$4.2 \mathrm{~kJ}$$8.4 \mathrm{~kJ}$Correct Option: , 4 Solution:...
Read More →A wooden wheel of radius
Question: A wooden wheel of radius $\mathrm{R}$ is made of two semicircular parts (see figure). The two parts are held together by a ring made of a metal strip of cross sectional area $\mathrm{S}$ and Length $\mathrm{L}$. $\mathrm{L}$ is slightly less than $2 \pi \mathrm{R}$. To fit the ring on the wheel, it is heated so that its temperature rises by $\Delta \mathrm{T}$ and it just steps over the wheel. As it cools down to surrounding temperature, it presses the semicircular parts together. If t...
Read More →In the above circuit the current in each resistance is :-
Question: In the above circuit the current in each resistance is :- $0.5 \mathrm{~A}$$0 \mathrm{~A}$$1 \mathrm{~A}$$0.25 \mathrm{~A}$Correct Option: , 2 Solution:...
Read More →The logic circuit shown below has the input wave forms
Question: The logic circuit shown below has the input wave forms ' $A$ ' and ' $B$ ' as shown. Pick out the correct output waveform. Correct Option: 1 Solution:...
Read More →When a current of 5 mA is passed through a galvanometer having a coil of
Question: When a current of $5 \mathrm{~mA}$ is passed through a galvanometer having a coil of resistance $15 \Omega$, it shows full scale deflection. The value of the resistance to be put in series with the galvanometer to convert it into to voltmeter of range $0-10 \mathrm{~V}$ is :-$2.535 \times 10^{3} \Omega$$4.005 \times 10^{3} \Omega$$1.985 \times 10^{3} \Omega$$2.045 \times 10^{3} \Omega$Correct Option: , 3 Solution:...
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