Power Delivered and Heat Dissipated in a Circuit

Q.

A resistor develops $500J$ of thermal energy in $20s$ when a current of $1.5A$ is passed through it. If the current is increased from$1.5A$ to $3A$, what will be the energy developed in the $20s$.

1. $500J$

2. $1000J$

3. $2000J$

4. $1500J$

Q. In the shown arrangement of the experiment of a meter bridge, if length of $\text{AC}$ corresponding to null deflection of galvanometer is $x$, what would be its value if the radius of the wire $\text{AB}$ is doubled ?

1. $x$
2. $\frac{x}{4}$
   
3. $4x$
4. $2x$

Q. A cell of emf $1.5V$ having a finite internal resistance is connected to a load resistance of $2\Omega$. For maximum power transfer, the internal resistance of the cell should be

1. $4\Omega$
2. $0.5\Omega$
3. $2\Omega$
4. None of these

Q. 48.The virtual current of 4A and 50Hz flows in an AC circuit containing a coil.The power consumed in the coil is 240W. If the virtual voltage across the coil is 100V, than its Resistance is

Q. Figure shows an ampereian path $\text{ABCDA}$. Part $\text{ABC}$ lies in vertical plane $\text{PSTU}$ while part $\text{CDA}$ lies in horizontal plane $\text{PQRS}$. $\oint \overrightarrow{B}.\overrightarrow{dl}$ for this path according to the Ampere's circuital law will be:

1. $(i_1-i_2+i_3){\mu }_0$
2. $(-i_1+i_2){\mu }_0$
3. $i_3{\mu }_0$
4. $(i_1+i_2){\mu }_0$

Q. An electric heater of power 100W raises the temperature of 5kg of a liquid from 25°c to 31°C in 2 min .calculate the specific heat of the liquid

Q. A storage battery is connected to a charger for charging with a voltage of $12.5\text{V}.$ The internal resistance of the storage battery is $1\Omega .$ When the charging current is $0.5A,$ the emf of the storage battery is

1. $13\text{V}$
2. $12.5\text{V}$
3. $12\text{V}$
4. $11.5\text{V}$

Q. A Zener diode is specified to have break-down voltage of $9.1\text{V}$ with a maximum power dissipation of $364\text{mW}.$ What is the maximum current that the diode can handle ?

1. $30\text{mA}$
2. $40\text{mA}$
3. $60\text{mA}$
4. $70\text{mA}$

Q. 65.A 25 watt_220 volt bulb and a 100watt_220volt bulb are connected in parallel across a 440 volt line which bulb will fuse or no one fuse and why

Q. The ratio of time constants in charging and discharging of inductor in the circuit shown in figure is

1. $1:1$
2. $3:2$
3. $2:3$
4. $1:3$

Q. A cell of constant emf first connected to a resistance $R_1$ and then connected to a resistance $R_2$. If power delivered in both cases is same, then the internal resistance of the cell is

1. $\sqrt{R_1{R}_2}$
2. $\sqrt{\frac{R_1}{R_2}}$
3. $\frac{R_1-R_2}{2}$
4. $\frac{R_1+R_2}{2}$

Q. if two bulbs 60W 250V and 120W 250V are connected in parallel across a 400V then bulb will be fused?

Q. A battery of emf E and internal resistance r is connected to a resistor of resistance $r_1$ and Q joules of heat is produced in a certain time t. When the same battery is connected to another resistor of resistance $r_2$ the same quantity of heat is produced in the same time t the value of r is

1. 
2. 
3. 
4. 

Q.

The Wheatstone bridge and its balance condition provide a practical method for the determination of ___________

Q. A capacitor of capacitance $10\mu \text{F}$ is charged by connecting it to a battery of emf $5\text{V}$. The capacitor is now disconnected and reconnected to the battery with the polarity reversed. Find heat developed in the connecting wires.

1. $50\text{mJ}$
2. $500\text{mJ}$
3. $50\mu \text{J}$
4. $500\mu \text{J}$

Q.

what is q factor of capacitor?

Q. A resistor R has power dissipation P with cell voltage E. The resistor is cut in n equal parts and all parts are connected in parallel with same cell. The new power dissipation is:

1. nP
2. $n^{2}P$
3. $\frac{n}{P}$
4. $n{P}^2$

Q. What is the power in the given circuit?

1. 3.6 W
2. 35 W
3. 175W
4. 245W

Q. A current $i=2\text{A}$ flows through the resistance $R=10\Omega$ with what constant speed $v$ (in m/s), the piston (mass $=1\text{kg}$) must move in upward direction so that temperature of ideal gas present inside cylinder may remain unchanged? Take ($g=10{\text{m/s}}^2$)

Q. A battery of emf $12\text{V}$ having $10\Omega$ internal resistance is connected with $100\Omega$ resistor. If the resistance of a resistor increases by $1\%$, while total power loss remains constant, what should be the percentage change in emf ?

1. $0.5\%$
2. $0.45\%$
3. $0.55\%$
4. $0.62\%$

Q.

A light bulb is rated at 125 W for a 250 V a.c., supply.
Calculate the resistance of the bulb.

Q. Emf applied and current in an AC circuit are volt and ampere respectively. Average power loss in the circuit is

Q.

A thermally insulated rigid container contains an ideal gas at ${27}^{o}C$. It is fitted with a heating coil of resistance 50$\Omega$. A current is passed through the coil for 10 minutes by connecting it to a d.c. source of 10 V. The change in the internal energy is

1. zero

2. 300 J

3. 600 J

4. 1200 J

Q. An electric bell has a rating of 500 W 100 V. It is used in a circuit having a 200 V supply. What resistance must be connected in series with the bulb so that it delivers 500 W?

1. 10 ohm
2. 20 ohm
3. 30 ohm
4. 40 ohm

Q. Consider two arrangements of $N$ identical resistors, one in parallel and the other in series. Each of these arrangements are connected to batteries of the same voltage. The ratio of power dissipated in the parallel arrangement to the series arrangement is

1. $N$
2. $\frac{1}{N}$
3. $N^2$
4. $\frac{1}{N^2}$

Q. A pure inductor, pure capacitor, and two pure equal resistors are connected as shown in the circuit, such that $L=2R^{2}C$.
At an instant $t=0$, the switch is closed. If $i_1$ and $i_2$ are currents shown in branches at some time $t=t_o$ relation $\frac{d{i}_1}{dt}+\frac{d{i}_2}{dt}=0$ is satisfied, then

1. $t_o=2RC\ln 2$
2. $t_o=4RC\ln 2$
3. $t_o=3RC\ln 2$
4. $t_o=3RC\ln 4$

Q. Two capacitors with capacitances $30\mu F\text{and}60\mu F$ are charged to potentials 20 V and 10 V respectively. Then they are disconnected from their respective batteries and connected to each other so that plates with same polarities connected together. The heat produced after the capacitors are connected as described is

1. 0.2 mJ
2. 1.0 mJ
3. 5 mJ
4. 0.5 mJ

Q. The power factor of the following circuit is

1. $\frac{1}{\sqrt{2}}$
2. $\frac{\pi }{4}$
3. $1$
4. $\sqrt{2}$

Q. Power dissipated in a resistor is to resistance when current through it is constant, and to resistance when voltage across it is constant.

1. proportional
2. inversely proportional
3. equal
4. unsusceptible

Q. An electric kettle has two coils. When one coil is connected to the AC mains the water in the kettle boils in 10 minutes. When the other coil is used the same quantity of water takes 15 minutes to boil. How long will it take for the same quantity of water to boil if the two coils are connected in parallel?

1. 24 min
2. 6 min
3. 12 min
4. 18 min