CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 8 - MCQExams.com

The supply voltage to a room is $$120\ V$$. The resistance of the lead wires is $$6\ \Omega$$. A $$60W,120V$$ bulb is already switched on. What is the decrease of voltage across the bulb, when a $$240 W,120V$$ heater is switched on in parallel to the bulb?
  • $$2.9$$ $$volt$$
  • $$13.3$$ $$volt$$
  • $$10.04$$ $$volt$$
  • $$zero\ volt$$
A $$220$$ volt, $$1000$$ watt bulb is connected across a $$110$$ volt mains supply. The power consumed will be.
  • $$750$$ watt
  • $$500$$ watt
  • $$250$$ watt
  • $$1000$$ watt
The resistance of a $$10m$$ long potentiometer wire is $$50\Omega$$. It is connected in series with a $$3V$$ battery and $$10\Omega$$ resistor. The potential difference between two points separated by distance $$40cm$$ is equal to ______
  • $$0.02V$$
  • $$0.1V$$
  • $$0.06V$$
  • $$1.2V$$
If the figure shows a part of an electric circuit, then the current $$I$$ is
1016741_6b588bda42de45c4bde49b47b2332494.PNG
  • $$1A$$
  • $$3A$$
  • $$2A$$
  • $$4A$$
If $${i}_{1}=3\sin{\omega t}$$ and $${i}_{2}=4\cos{\omega t}$$, then $${i}_{3}$$ is -
1021440_60f5b332b2ee4a11a4500ea0432a5ce5.png
  • $$5\sin{(\omega t+{53}^{o})}$$
  • $$5\sin{(\omega t+{37}^{o})}$$
  • $$5\sin{(\omega t+{45}^{o})}$$
  • $$5\cos{(\omega t+{53}^{o})}$$
A solid spherical conducting shell has inner radius $$a$$ and outer radius $$2a$$. At the centre of the shell a point charge $$+Q$$ is located. What must be the charge of the shell be in order for the charge density on the inner and outer surfaces of the shell to be exactly equal?
1026888_f6e3330c09964e12b1a591640cc085e8.png
  • $$-5Q$$
  • $$+3Q$$
  • $$-4Q$$
  • $$+4Q$$

Consider a cube as shown in the fig-1; with uniformly distributed charge within its volume. The potential at one of its vertex P is $${V_0}$$.A cubical portion of half the size (half edge length) of the original cube is cut and removed as shown in the fig-Find the modulus of potential at the point P in the new structure. 


1026679_89861f650228459494da9b7c7bf6693b.png
  • $${{7} \over 8}{V_0}$$
  • $${{{V_0}} \over 2}$$
  • $${{3{V_0}} \over 4}$$
  • $${{{V_0}} \over 4}$$
The number of turns in th coil of an $$ac$$ generator is $$5000$$ and the area of the coil is $$0.25\ {m}^{2}$$. The coil is rotated at the rate of $$100$$ cycles/s in a magnetic field of $$0.2\ T$$. The peak value of emf generated is nearly:
  • $$786\ kV$$
  • $$440\ kV$$
  • $$220\ kV$$
  • $$157.1\ kV$$

A potentiometer has a wire of 100 cm length and its resistance is 10 ohms. It is connected in series with a resistance of 40 ohms and a battery of emf 2 V  and negligible internal resistance. If a source of  unknown emf E connected in the secondary is balanced by 40 cm length of potentiometer wire, the value of E is:
  • 0.2 V
  • 0.4 V
  • 0.08 V
  • 0.16 V
Refer to teh circuit shown. What will be the total power dissipation in the circuit if $$P$$ is the power dissipated in $${R}_{1}$$? It is given that $${R}_{2}=4{R}_{1}$$ and $${R}_{3}=12{R}_{1}$$
1028158_9490e31283ea4eb58a741eee56a3ca02.png
  • $$4P$$
  • $$7P$$
  • $$13P$$
  • $$17P$$
A potentiometer wire of $$10\ m$$ length and having a resistance of $$1\ ohm/m$$ is connected to an accumulator of emf $$2.2$$ volt and a high resistance box. To obtain a potential gradient of $$2.2mV/m$$, the value of resistance used from the resistance box is :-
  • $$790\ ohm$$
  • $$810\ ohm$$
  • $$990\ ohm$$
  • $$1000\ ohm$$
The temperature coefficient of resistance of wire is $$12.5 \times 10^{-4} / C^0$$. At 300K the resistance of the wire is 1 ohm. The temperature at which resistance will be 2 ohm is
  • 1154K
  • 1100K
  • 1400K
  • 1127K

For the following circuits, the potential difference between
X and Y in volt is $$\left( {{V_x} - {V_y}} \right)$$


1043163_8009f5fd84634aafa5efb62cb3ffc698.png
  • 1
  • -1
  • 2
  • -2
Write T against true and F against false in the statements.
A charged glass road attract a charged plastic straw
  • True
  • False
If current $$I_1 = 3A$$ sin $$\omega t$$ and $$I_2 = 4A$$ cos $$\omega t$$, then $$I_3$$ is :
1046047_91e72dfeae304255ab578b157cc36a73.png
  • $$5A sin (\omega t + 53^0)$$
  • $$5A sin (\omega t + 37^0)$$
  • $$5A sin (\omega t + 45^0)$$
  • $$5A sin (\omega t + 30^0)$$
 In the circuit shown, the current in the $$1
ohm$$ resistor is:
1036746_d8aa134d30fb46f5977a3b563757529c.png
  • $$ 0.13A, $$ from Q to P
  • $$0.13A, $$ from P to Q
  • $$ 1.3A, $$ from P to Q
  • $$ 0A, $$
In the diagram shown $$P$$ is a point negative charge. It's weight is balanced by the electric force due to the fixed very long wire. The equilibrium of the particle is
1063098_3ac4799f160841b396ec705bed667edb.png
  • Stable for vertical displacements
  • Neutral for vertical displacements
  • Stable for horizontal displacements (parallel to the wire)
  • Neutral for horizontal displacements (parallel to the wire)
Find the potentials of points A and B:-
1066581_e88bd68347b5405aa5c47a199c425099.png
  • $$V_A = + 10 \ V; V_B = 0 \ V$$
  • $$V_A = + 7.5 \ V; V_B = - 2.5 \ V$$
  • $$V_A = + 2.5 \ V; V_B = - 7.5 \ V$$
  • $$V_A = + 0 \ V; V_B = - 10 \ V$$
If the resistance in the circuit is increased four times by keeping the potential difference the same, the current in the circuit is ___________.
  • Remains same
  • Four times
  • One fourth
  • Half
$$AB$$ is part of a circuit as shown, that absorbs energy at a rate of $$50 \ W$$. $$E$$ is an electromotive force device that has no internal resistance.
1087383_52b5727ee0fb4984bc0c9879b84b95e1.JPG
  • Potential difference across $$AB$$ is $$48 V$$
  • Electromotive force device is $$48 V$$.
  • Point $$B$$ is connected to the positive terminal of $$E$$.
  • Rat of conversion from electrical to chemical energy is $$48 W$$ in device $$E$$.
Charges $$ 25Q,9Q$$ and $$Q$$ are placed at point $$ABC$$ such that $$AB=4m$$, $$BC=3m$$ and angle between $$AB$$ and $$BC$$ is $$90^\circ$$. then force on the charge $$C$$ is:
  • Zero
  • $$\frac{q^2}{{\pi { \in _0}\sqrt 5 }}$$
  • $$\frac{{2{Q^2}}}{{\pi { \in _0}}}$$
  • $$\frac{{5{Q^2}}}{{4\pi { \in _0}}}$$
The $$V-I$$ graph for a conductor at temperature $$T_{1}$$ and $$T_{2}$$ are as shown in figure. The term $$(T_{2}-T_{1})$$ is proportional to:
1079367_95d8343e4307445f8b93cbc8616ec65e.png
  • $$\cos 2\theta$$
  • $$\sin 2\theta$$
  • $$\cot 2\theta$$
  • $$\tan 2\theta$$
An electric motor operates on a $$50 \ V$$ supply and a current of $$1 \ A $$. If the efficiency of the motion is $$30 \ \%$$, what is the resistance of winding of motion ?
  • $$35 \ \Omega$$
  • $$4 \ \Omega$$
  • $$2.9 \ \Omega$$
  • $$3.1\  \Omega$$
Potentiometer wire Pq of length 1m is connected to a standard cell $$ E_1 $$ Another cell of E2 of emf1.02v/s connected as shown in the circuit diagram with a resistance 'r' and with a switch 's' . With the switch  S open, null position is obtained at a distance of 51 cm from p,Calculate
  • emf of the cell.
  • Potential gradient of the wire.
  • When switch S is closed, will null point moves towards p or Q?
  • insufficient data
Potentiometer is based on
  • Deflection method
  • Zero deflection method
  • Both (a) and (b)
  • None of these
Two cells each of electromotive force $$E$$ and internal resistance $$r$$ are concerned in parallel across the resistance $$R$$. The maximum energy given to the resistor per second if:
  • $$R = \dfrac{r}{2}$$
  • $$R = r$$
  • $$R = 2r$$
  • $$R = 0$$
The wire of potentiometer has resistance $$4 \Omega$$ and length $$1 m$$. It is connected to a coil of electromotive force $$2$$ volt and internal resistance $$1 \Omega$$. If a cell of electromotive force $$1.2$$ volt is balanced by it, the balancing length will be:
  • $$90 \ cm$$
  • $$60 \ cm$$
  • $$50 \ cm$$
  • $$75 \ cm$$
For comparing the electromotive force of two cells with a potentiometer, a standard cell is used to develop a potential gradient along the wire. Which of the following possibilities would make the experiment unsuccessful?
  • The electromotive force system of the standard cell is larger than the $$E$$ electromotive force system of the two cells.
  • The diameter of the wires is the same and uniform throughout
  • The number of wires is ten
  • The electromotive force of the standard cell is smaller than the electromotive force of the two cells.
Two identical batteries, each of electromotive force $$2 V$$ and internal resistance $$r = 1 \Omega$$ are connected as shown. The maximum power that can be developed across $$R$$ using these batteries is:
1098583_b293159296b249398ac22236b72b7aa2.png
  • $$2 W$$
  • $$3.2 W$$
  • $$8,2 W$$
  • $$4 W$$
$$n$$ identical cells each of electromotive force $$e$$ and internal resistance $$r$$ are connected in series of this combination. The current through $$V$$ is:
  • $$\frac{{2e}}{n}$$
  • $$\dfrac{n \space e}{nR + r}$$
  • $$\dfrac{e}{R + nr}$$
  • $$\dfrac{n \space e}{R + r}$$
A resistor of resistance $$1000 \Omega$$ is connected to an AC source $$E=220 V sin(100 \pi  rad/s$$ . the power consumed by resistor is
  • $$48.4 W$$
  • $$24.2 W$$
  • $$12.1 W$$
  • ZERO
For an AC Circuit, the potential difference and current are given by $$V=10\sqrt { 2 } \sin { \omega t } $$ (inV) and $$I=2\sqrt { 2 } \cos { \omega t }$$ (in A) respectively.The power dissipated in the instrument is:
  • $$20W$$
  • $$40W$$
  • $$40\sqrt { 2 }W$$
  • Zero
Eight resistances each of resistance $$5\Omega $$ are connected in the circuit as shown in figure. The equivalent resistance between $$A$$ and $$B$$ is
1113134_1cdebc466273425eb0e244de5d046333.png
  • $$\dfrac{8}{3}\Omega $$
  • $$\dfrac{16}{3}\Omega $$
  • $$\dfrac{15}{7}\Omega $$
  • $$\dfrac{19}{2}\Omega $$
Two resistances of $$400\Omega$$ and $$800\Omega$$ are connected in series with a $$6$$ volt battery of negligible internal resistance. A voltmeter of resistance $$10,000\Omega$$ is used to measure the potential difference across $$400\Omega$$. The error in the measurement of the potential difference in volts approximately is :
  • $$0.01$$
  • $$0.02$$
  • $$0.03$$
  • $$0.05$$
If $${i_1} = 3\sin \omega t\,and\,{i_2} = 4\cos \omega t$$, then $$i_3$$ is
1121363_dcdbdb64e95c488a901a2994868c64e9.PNG
  • $$5\sin \left( {\omega t + {{53}^ \circ }} \right)$$
  • $$5\sin \left( {\omega t + {{37}^ \circ }} \right)$$
  • $$5\sin \left( {\omega t + {{45}^ \circ }} \right)$$
  • $$5\cos \left( {\omega t - {{53}^ \circ }} \right)$$
In wheatstone's bridge $$P = 9$$ ohm, $$ R = 4 $$ ohm and $$ S = 6 $$ ohm. How much resistance must be put in parallel to the resistance S to balance the bridge?
  • $$24$$ ohm
  • $$13.5$$ ohm
  • $$7.2$$ ohm
  • $$18.7$$ ohm

A circular coil of area $$8{m^2}$$  and number of turns 20 is placed in a magnetic field of 2T with its plane perpendicular to it. It is rotated with an angular velocity of 20rev/s about its natural axis. The emf induced is
  • $$400 V$$
  • $$800\pi V$$
  • $$Zero$$
  • $$400\pi V$$
In the following diagram, the deflection in the galvanometer in a potentiometer
circuit is zero, then 
1145121_d08ac4852753413caa6ea6d7a9e82ef2.png
  • $${E_1} > {E_2}$$
  • $${E_2} > {E_1}$$
  • $${E_1} = {E_2}$$
  • $${E_1} + {E_2} = E$$
At what  temperature will the resistance of a copper wire become three times its value at $$0^{0}$$ C? [Temperature coefficient of resistance for copper = $$4\times 10^{-3}per^{0}C$$]:-
  • $$500^{0}C$$
  • $$450^{0}C$$
  • $$600^{0}C$$
  • None of these
Taking the electric charge 'e' and permittivity $$\epsilon$$ .use dimensional analysis to determine the correct expression for Wp. Where Wp $$\rightarrow $$ angular frequency N $$\rightarrow $$ number of density of free electron, m $$\rightarrow $$ mass
  • $$\sqrt{\dfrac{Ne}{m\epsilon}}$$
  • $$\sqrt{\dfrac{me}{N\epsilon}}$$
  • $$\sqrt{\dfrac{Ne^2}{m\epsilon}}$$
  • $$\sqrt{\dfrac{Ne^3}{m\epsilon}}$$
Wattless current in the circuit is
1126927_0b059c0a9219440c978d8383ea4b13d0.png
  • 3.75 A
  • 5 A
  • 2.1 A
  • zero
Three resistances $$R_1,R_2$$ & $$R_3$$ $$(R_1> R_2> R_3)$$ are connected in series. If current $$I_1,I_2$$ & $$I_3$$ respectively is flowing through them, the correct relation will be
  • $$I_1=I_2=I_3$$
  • $$I_1> I_2> I_3$$
  • $$I_1< I_2< I_3$$
  • $$I_1> I_2< I_3$$
The inductance of a coil is $$L = 10 H$$ and resistance $$R = 5 \Omega$$. If applied voltage of battery is $$10 V$$ and it switches off in $$1$$ millisecond, find induced electromotive force of inductor.
  • $$2 \times 10^4 V$$
  • $$1.2 \times 10^4 V$$
  • $$2 \times 10^{-4} V$$
  • None of these
If the circuit shown in the figure, the internal resistance of the battery is $$1.5\Omega$$ and $${V}_{p}$$ and $${V}_{Q}$$ are potentials at $$P$$ and $$Q$$ respectively. What is the potential difference between the points $$P$$ and $$Q$$
1138408_1b85dcbdf72a4349bd73c533d5a3ced0.png
  • $$Zero $$
  • $$4\ volt\ \left({V}_{p}>{V}_{Q}\right)$$
  • $$4\ volt\ \left({V}_{Q}>{V}_{P}\right)$$
  • $$2.5\ volt\ \left({V}_{Q}>{V}_{P}\right)$$
In the given figure, if the heat flowing through the 5 $$ohm$$ resistance is 10 calorie then how much heat is flowing through the 4 $$ohm$$ resistance ?
1126595_ad43ea590f614b86a8256bf284a4f71d.png
  • 1 calorie
  • 2 calorie
  • 3 calorie
  • 4 calorie
An electron is rotating around an infinite positive linear charge in a circle of radius 0.1 m, if the linear charge density is $$ 1 \mu C/m, $$ then the velocity of electron in m/s will be
  • $$ 0.562 \times 10^7 $$
  • $$ 5.62 \times 10^7 $$
  • $$ 562 \times 10^7 $$
  • $$ 0.0562 \times 10^7 $$
A $$3hp$$ motors requires $$2.4 kw$$ to drive it; its efficiency is about:
  • $$90$$%
  • $$75$$%
  • $$60$$%
  • $$50$$%
For which of the following substances the resistance decreases with the decrease in temperature:
  • Germanium
  • Silicon
  • Silver
  • None
The temperature coefficient of resistance of a wire is 0.00125 per degree celcius. At 300 K its resistance of the wire is 2 ohms. The temperature when resistance doubles is :-
  • 1154 K
  • 1100 K
  • 600 K
  • 1400 K
The name of the instrument which records electrical energy consumed by customer is
  • Ampere-hour meter
  • Watt-hour meter
  • Var-hour meter
  • Volt-ampere meter
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Class 12 Medical Physics Quiz Questions and Answers