CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 7 - MCQExams.com

Which of the following shows energy changes that takes place when an incandescent bulb glows using a battery?
  • Chemical>Electrical>heat>Light energy
  • Electrical>Chemical>Light>heat energy
  • Chemical>Electrical>Heat energy
  • Electrical>Chemical>Light energy
A potentiometer circuit shown in the figure is set up to measure emf of cell E. As the point P moves from X to Y, the galvanometer G shows deflection always in one direction, but the deflection decreases continuously until Y is reached. The balance point between X and Y maybe obtained by
617141_21725494d23f445a8d54194c1240a848.png
  • Decreasing the resistance R and decreasing V
  • Decreasing the resistance R and increasing V
  • Increasing the resistance R and increasing V
  • Increasing the resistance R and decreasing V
In specific resistance measurement of a wire using a meter bridge, the key k in the main circuit is kept open when we are not taking readings. The reason is
  • the emf of cell will decrease.
  • the value of resistance will change due to joule heating effect.
  • the galvanometer will stop working.
  • none of these.
If $$i_{1}=3\sin\omega t$$ and $$i_{2}=4\cos\omega t$$, then $$i_{3}$$ is
617148_942995742fb144329864638735ee81ff.png
  • $$\displaystyle5\sin \left ( \omega t+53^{\circ} \right )$$
  • $$\displaystyle5\sin \left ( \omega t+37^{\circ} \right )$$
  • $$\displaystyle5\sin \left ( \omega t+45^{\circ} \right )$$
  • $$\displaystyle5\cos \left ( \omega t+53^{\circ} \right )$$
Steady current flows in a metallic conductor of non-uniform cross-section. Which of the following quantities is a constant along the conductor ?
  • Current
  • Current density
  • Electric field
  • Drift speed
A voltmeter having a resistance of $$998\Omega$$ is connected to a cell of emf $$2$$V and internal resistance $$2\Omega$$. The error in the measurement of emf will be.
  • $$4\times 10^{-1}$$V
  • $$2\times 10^{-3}$$V
  • $$4\times 10^{-3}$$V
  • $$2\times 10^{-1}$$V
In a potentiometer of wire length $$l$$, a cell of emf V is balanced at a length $$\dfrac{l}{3}$$ from the positive of the wire. For another cell of emf $$1.5 V$$, the balancing length becomes
  • $$\dfrac{l}{6}$$
  • $$\dfrac{l}{2}$$
  • $$\dfrac{l}{3}$$
  • $$\dfrac{2l}{3}$$
  • $$\dfrac{4l}{3}$$
The resistance of a bulb filament is $$100\Omega$$ at a temperature at $$100^{o}C$$. If its temperature coefficient of resistance be $$0.005/^{o}C$$, then its resistance will become $$200\Omega$$ at a temperature of
  • $$300^{o}C$$
  • $$400^{o}C$$
  • $$500^{o}C$$
  • $$200^{o}C$$
Figure below shows a portion of an electric circuit with the currents in amperes and their directions. The magnitude and direction of the current in the portion $$PQ$$ is
632884_f353d27ba5124f6c9deca4559312c3dd.png
  • $$0 A$$
  • $$3 A$$ from $$P$$ to $$Q$$
  • $$4 A$$ from $$Q$$ to $$P$$
  • $$6 A$$ from $$Q$$ to $$P$$
The best instrument for accurate measurement of emf of a cell.
  • Potentiometer
  • Wheatstone Bridge
  • Voltmeter
  • Ammeter 
In Wheatstone's bridge, three resistors P, Q, R are connected in three arms in order and $$4^{th}$$ arm is formed by two resistors $$s_1$$ and $$s_2$$ connected in parallel. The condition for bridge to be balanced is $$\displaystyle\frac{P}{Q}=$$.
  • $$\displaystyle\frac{R(s_1+s_2)}{s_1s_2}$$
  • $$\displaystyle\frac{s_1s_2}{R(s_1+s_2)}$$
  • $$\displaystyle\frac{Rs_1s_2}{(s_1+s_2)}$$
  • $$\displaystyle\frac{(s_1+s_2)}{Rs_1s_2}$$
An electron in potentiometer wire experiences a force $$2.4\times 10^{-19}$$N. The length of potentiometer wire is $$6m$$. The e.m.f. of the battery connected across the wire is (electronic charge $$=1.6\times 10^{-19}$$C).
  • $$6$$V
  • $$9$$V
  • $$12$$V
  • $$15$$V
A potentiometer wire of length $$10 m$$ is connected in series with a battery. The e.m.f. of a cell balances against $$250 cm$$ length of wire. If length of potentiometer wire is increased by $$1 m$$, the new balancing length of wire will be
  • $$2.00 m$$
  • $$2.25 m$$
  • $$2.50 m$$
  • $$2.75 m$$
A student's $$9.0V, 7.5W$$ portable radio was left on from $$9:00\ P.M.$$ until $$3:00 A.M.$$ How much charge passed through the wires?
  • $$18000C$$
  • $$24000C$$
  • $$6000C$$
  • $$12000C$$
A potentiometer is an ideal device of measuring potential difference because
  • It uses a sensitive galvanometer
  • It is an elaborate arrangement
  • It has a long wire hence heat developed is quickly radiated
  • It does not disturb the potential difference it measures
To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell.
  • True
  • False
In a potention meter of one metre length an unknown emf voltage source is balanced at 60 cm length of potention meter wire, while a 3v battery is balanced at 45 cm length. Then, the emf of the unknown voltage source is :
  • 3 V
  • 2.25 V
  • 4 V
  • 4.5 V
A cylindrical conductor is placed near other positively charged conductor. The net charge acquired by the cylindrical conductor will be :
  • Positive only
  • Negative only
  • Zero
  • Either positive or negative
In potentiometer experiment, null point is obtained at a particular point for a cell on potentiometer wire x cm long. If the length of the potentiometer wire is increased without changing the cell, the balancing length will (Driving source is not changed)
  • increase
  • decrease
  • not change
  • becomes zero
Five cells each of internal resistance $$ 0.2 \Omega $$ and emf $$ 2 V$$ are connected in series with a resistance of $$ 4\Omega $$.The current through the external resistance is 
  • $$ 4 A$$
  • $$ 2 A $$
  • $$ 1 A$$
  • $$ 0.5 A$$
Ten identical batteries each of emf 2 V are connected in series to a $$8 \Omega$$ resistor. If the current in the circuit is 2 A, then the internal resistance of each battery is
  • $$0.2 \Omega$$
  • $$0.3 \Omega$$
  • $$0.4 \Omega$$
  • $$0.5 \Omega$$
  • $$1 \Omega$$
In a potentiometer arrangement, a cell of emf $$1.5V$$ gives a balance point at $$27cm$$ length of wire. If the cell is replaced by another cell and balance point shifts to $$54cm$$, the emf of the second cell is
  • $$3V$$
  • $$1.5V$$
  • $$0.75V$$
  • $$2.25V$$
Kirchhoff's first law ie, $$\displaystyle \Sigma i=0$$ at a junction is based on the law of conservation of
  • Charge
  • Energy
  • Momentum
  • Angular momentum
A potentiometer wire of length $$L$$ and resistance $$10\Omega$$ is connected in series with a battery of e.m.f. $$2.5\ V$$ and a resistance in its primary circuit. The null point corresponding to a cell of e.m.f. $$1\ V$$ is obtained at a distance $$L/2$$. If the resistance in the primary circuit is doubled then the position of new null point will be
697539_7f35a66b0a804676aa2300d3fef0ffd8.jpg
  • $$0.4\ L$$
  • $$0.5\ L$$
  • $$0.6\ L$$
  • $$0.8\ L$$
If specific resistance of a potentiometer wire is $$10^{-7}\Omega m$$ and current flowing through it is $$0.1\ amp$$., cross-sectional area of wire is $$10^{-6}m^{2}$$ then potential gradient will be
  • $$10^{-2}volt/m$$
  • $$10^{-4}volt/ m$$
  • $$10^{-6}volt/ m$$
  • $$10^{-8}volt/ m$$
36 identical cell each having emf 1.5 volt and internal resistance $$ 0.5 \Omega$$ are connected in series with an external resistance of $$12 \Omega$$ .If 6 cells are wrongly connected then current through the circuit will be 
  • 1.2 A
  • 1 A
  • 2 A
  • 4 A
A potentiometer wire of length $$1m$$ has a resistance of $$100\Omega $$. It is connected in series with a resistance and a battery of emf $$2V$$ of negligible resistance. A source of emf $$10mV$$ is balanced against a length of $$40cm$$ of the potentiometer wire. What is the value of the external resistance.
  • $$890\Omega $$
  • $$7900\Omega $$
  • $$680\Omega $$
  • $$740\Omega $$
Observe the given figure and answer the following questions. The bulb will glow when a ______ is placed in between the probes.
809844_e790ef2d76374ef7837ca5b1298464e5.png
  • Crayon
  • Comb
  • Key
  • Piece of stone
Ravi connected three bulbs with the cells and a switch as shown. When switch is moved to ON position.
809850_cb6100c978054f9f9cbe2e5ef2963ae0.jpeg
  • The bulb X will glow first.
  • The bulb Y will glow first.
  • The bulbs Z and X will glow first.
  • All the bulbs will glow simultaneously.
Which of the following circuit diagram represents the given torch?
810212_a4c2351c8ed44cb28d3cfdbc23134ebe.png
What is the value of unknown resistance R, of galvanometer shows null deflection in the given meter bridge set up shown in the fig?
941984_79bc0e16c6ca424485f8b3b8e4e9453e.png
  • $$97.50\Omega$$
  • $$105\Omega$$
  • $$220\Omega$$
  • $$110\Omega$$
An electric heater is connected to the voltage supply. After a few seconds, current get its steady value then its initial current will be?
  • Equal to its steady current
  • Slightly higher than its steady current
  • Slightly less than its steady current
  • Zero
In Fig.,value of $${ I }_{ x }and\quad { I }_{ y }$$ are respectively
1545884_fee7b63518d149b4bb92776c152df142.png
  • 1A,1A
  • 1.2A,1.2A
  • 0.8A,0.8A
  • 1A,1.2A
In a meter bridge experiment, the ratio of the left gap resistance to right gap resistance is $$2 : 3$$, the balance point from left is?
  • $$60$$cm
  • $$50$$cm
  • $$40$$cm
  • $$20$$cm
Which of the following I-V graph represents ohmic conductors?
In the circuit shown in figure heat developed across $$2\Omega, 4\Omega$$ and $$3\Omega$$ resistances are in the ratio of.
941778_16548cd4b74a457cb15cda872a3283a0.png
  • $$2 : 4 : 3$$
  • $$8 : 4 : 12$$
  • $$4 : 8 : 27$$
  • $$8 : 4 : 27$$
The battery of a trunk has an emf of $$24$$V. If the internal resistance of the battery is $$0.8\Omega$$. What is the maximum current that can be drawn from the battery?
  • $$30$$A
  • $$32$$A
  • $$33$$A
  • $$34$$A
Figure (a) and figure (b) both are showing the variation of resistivity $$(\rho)$$ with temperature (T) for some materials. Identify the type of these materials.
941756_71954f2f9ff94c51a773cfa5f375798e.PNG
  • Conductor and semiconductor
  • Conductor and Insulator
  • Insulator and semiconductor
  • Both are conductors
In a Wheatstone bridge if the battery and galvanometer are interchanged then the deflection in galvanometer will:
  • Change in previous direction
  • Not change
  • Change in opposite direction
  • None of these
Point out the right statements about the validity of Kirchhoff's junction rule.
  • It is based on conservation of charge
  • Outgoing currents add up and are equal to incoming currents at a junction
  • Bending or reorienting the wire does not change the validity of Kirchhoff's junction rule
  • All of above
A circuit has a section ABC as shown in figure. If the potentials at points A, B and C are $$V_1, V_2$$ and $$V_3$$ respectively. The potential at point O is?
941946_e48560c8df6846149402de60b33cfba9.PNG
  • $$V_1+V_2+V_3$$
  • $$\left[\dfrac{V_1}{R_1}+\dfrac{V_2}{R_2}+\dfrac{V_3}{R_3}\right]\left[\dfrac{1}{R_1}+\dfrac{1}{R_2}+\dfrac{1}{R_3}\right]^{-1}$$
  • Zero
  • $$\left[\dfrac{V_1}{R_1}+\dfrac{V_2}{R_2}+\dfrac{V_3}{R_3}\right](R_1+R_2+R_3)$$
When an uncharged body touches a charged body, the 
  • Uncharged body acquires a similar charge.
  • Uncharged body acquires an equal and opposite charge
  • Charges body loses its charge
  • Uncharged body remains uncharged
In a potentiometer the balancing with a cell is at length of $$220$$cm. On shunting the cell with a resistance of $$3\Omega$$ balance length becomes $$130$$cm. What is the internal resistance of this cell?
  • $$4.5\Omega$$
  • $$7.8\Omega$$
  • $$6.3\Omega$$
  • $$2.08\Omega$$

$$3$$V potentiometer used for the determination of internal resistance of a $$2.4$$V cell. The balance point of the cell is open circuit is $$75.8$$cm. When a resistor of $$10.2\Omega$$ is used in the external circuit of the cell the balance point shifts to $$68.3$$cm length of the potentiometer wire. The internal resistance of the cell is?
941992_0c10c2629ec74ef4893d74be1e7a9a24.png
  • $$2.5\Omega$$
  • $$2.25\Omega$$
  • $$1.12\Omega$$
  • $$3.2\Omega$$
Which pair is not correct for the instrument used in the laboratory and their uses from the following?
InstrumentUses
(A)VoltmeterTo measure the electric potential difference 
(B)AmmeterTo measure the electric current
(C)GalvanometerTo detect the presence of current
(D)ResistorTo supply the electric energy to circuit
  • A
  • B
  • C
  • D
In the circuit shown, the value of currents $$I_{1}, I_{2}$$ and $$I_{3}$$ are
950029_f29ca818735d4282a78de8f005886d7f.png
  • $$3\ A, \dfrac {-3}{2}A, \dfrac {9}{2}A$$
  • $$\dfrac {9}{2}A, 3\ A, \dfrac {-3}{2}A$$
  • $$5\ A, 4\ A, -3\ A$$
  • $$7\ A, \dfrac {5}{4}A, \dfrac {9}{2}A$$
In a potentiometer a cell of emf $$1.5$$V gives a balanced point at $$32$$cm length of the wire. If the cell is replaced by another cell then the balance point shifts to $$65.0$$cm then the emf of second cell is?
  • $$3.05$$V
  • $$2.05$$V
  • $$4.05$$V
  • $$6.05$$V
Two cells of emf's approximately $$5$$V and $$10$$V are to be accurately compared using a potentiometer of length $$400$$cm.
  • The battery that runs the potentiometer should have voltage of $$8$$V
  • The battery of potentiometer can have a voltage of $$15$$V and R adjusted so that the potential drop across the wire slightly exceeds $$10$$V
  • The first portion of $$50$$cm of wire itself should have a potential drop of $$10$$V
  • Potentiometer is usually used for comparing resistances and not voltages
Consider a neutral conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then,
  • negative and distribute uniformly over the surface of the sphere
  • negative and appears only at the sphere closest to the point charge
  • negative and distribute non-uniformly over the entire surface of the sphere
  • zero
Which of the following statements is false?
  • Kirchhoff's second law represents energy conservation.
  • Wheatstone bridge is the most sensitive when all the four resistances are of the same order of magnitude.
  • In a balanced Wheatstone bridge if the cell and the galvanometer are exchanged, the null point is disturbed.
  • A rheostat can be used as a potential divider.
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Practice Class 12 Medical Physics Quiz Questions and Answers