CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 5 - MCQExams.com

A cell of e.m.f. $$\varepsilon$$ and internal resistance $$r$$ sends current $$1.0 A$$ when it is connected to an external resistance $$1.9\, \Omega$$. But it sends current $$0.5 A$$ when it is connected to an external resistance $$3.9\, \Omega$$. Calculate the values of $$\varepsilon$$ and $$r$$.
  • $$\varepsilon\, =\, 2.0\, V,\quad\, r\, =\, 0.1\, \Omega$$
  • $$\varepsilon\, =\, \, .1 V,\quad\, r\, =\, 2.0\, \Omega$$
  • $$\varepsilon\, =\, \, .2 V,\quad\, r\, =\, 1.0\, \Omega$$
  • Data insufficient
In our household applications, commercial unit of electricity is used. One unit is equal to:
  • $$1\ kW$$
  • $$1\ kWh$$
  • $$1\ kW/h$$
  • $$1\ Wh$$
What is the approximate resistance setting of a rheostat in which $$650 \  mA$$ of current flows with a $$150 \ V$$ source?
  • $$230 \ \Omega$$
  • $$56 \ \Omega$$
  • $$15 \ \Omega$$
  • $$13 \ \Omega$$
The four wires from a larger circuit intersect at junction A a shown. What is the magnitude and direction of the current between points A and B?
203126_3147ec45d5cb43bca9ad0fe614952201.png
  • 2 A from A to B
  • 2 A from B to A
  • 3 A from A to B
  • 3 A from B to A
The resistance of a copper wire and an iron wire at 20C are 4.$$\Omega $$ and 3.9$$\Omega $$ respectively. Neglecting any thermal expansion, find the temperature at which resistances of bolh are equal. 
$$\alpha _{ cu }=4.0\times { 10 }^{ -3 }{ K }^{ -1 }$$. and $$\alpha _{ fe }=4.0\times { 10 }^{ -3 }{ K }^{ -1 }$$.
  • $${ 65 }^{ o }C$$
  • $${ 75 }^{ o }C$$
  • $${ 270 }^{ o }C$$
  • $${ 95 }^{ o }C$$
Name the quantity which is measured in $$eV$$.
  • Power
  • Energy
  • Charge
  • Electric potential
Sensitivity of potentiometer can be increased by
  • increasing the e.m.f. of the cell.
  • increasing the length of the potentiometer.
  • decreasing the length of the potentiometer wire.
  • none of these.
The current $$I$$ and voltage $$V$$ graphs for a given metallic wire at two different temperatures $$T_1$$ and $$T_2$$ are shown in the figure. It is concluded that :

201003_f2a16de9d43b4910899b70024dac9e0e.png
  • $$T_1 > T_2$$
  • $$T_1 < T_2$$
  • $$T_1 = T_2$$
  • $$T_1 = 2 T_2$$
If in the experiment of Wheatstone's bridge, the positions of cells and galvanometer are interchanged, then balance point will
  • change
  • remain unchanged
  • depend on the internal resistance of cell and resistance of galvanometer
  • none of these
A potentiometer consists of a wire of length 4m and resistance 10$$\Omega$$. It is connected to a cell of e.m.f. 3V. The potential gradient of wire is
  • 0.75 V/m
  • 2 V/m
  • 6 V/m
  • 10 V/m
Substances which allow electricity to pass through them are known as
  • Electrical conductors
  • Electrical insulators
  • Both conductors & insulators
  • None of these
State whether true or false.
Bulbs C and D are connected in series.

269482_27d142d124d94b18a3307b53ee495dda.png
  • True
  • False
Substances that do not allow free flow of charge through them are called __________.
  • Insulators
  • Conductors
  • Both A and B
  • None of these
The principle involved in potentiometer is
  • variation of current with variati wire on in the diameter of the potentiometer
  • similar to the principle of Wheatstone bridge
  • variation of resistance with temperature
  • both (a) and (b)
The given figure is a 'material tester'.
Which of the following objects will make the bulb glow when put on the gap shown?
265824_578760a25a9145acb3ba47edae831376.png
If we touch a naked current carrying wire, we get a shock. This is because our body is a :
  • conductor of electricity
  • insulator of electricity
  • source of electricity
  • both B&C
Value of Current i in the following circuit is :-
278185.png
  • 13 A
  • 12 A
  • 9 A
  • None of these
A group of N cells whose emf varies directly with the internal resistance as per the equation $$E_{N}=1.5r_{N}$$ are connected as shown in the figure. The current I in the circuit is :-

279306.png
  • 5.1 A
  • 0.51 A
  • 1.5 A
  • 0.15 A
In a typical Wheatstone network the resistance in cyclic order are $$A=10\:\Omega ,\:B=5\:\Omega ,\:C=4\:
\Omega $$ and $$D=4\:\Omega $$ for the bridge to be balanced :-

279138.png
  • $$10\:\Omega $$ should be connected in parallel $$A$$
  • $$10\:\Omega $$ should be connected in series with $$A$$
  • $$5\:\Omega $$ should be connected in series with $$B$$
  • $$5\:\Omega $$ should be connected in parallel with $$B$$
At what temperature will the resistance of a copper wire become three times its value at $$0^{\circ}C$$ [Temperature coefficient of resistance for copper $$=4\times 10^{-3}per^{\circ}C$$] :-
  • $$400^{\circ}C$$
  • $$450^{\circ}C$$
  • $$500^{\circ}C$$
  • $$550^{\circ}C$$
Referring to the circuit, $$R$$ is the resistance of a potentiometer. As the sliding contact is moved from $$a$$ to $$b$$ the reading in the ideal ammeter will :

290232_39d69c751f1542fcbcf4e577f0d12e9d.png
  • increase
  • decrease
  • initial decrease and then increase
  • initially increase and then decrease
Which of the statement is wrong :-
  • when all resistance are equal, then the sensitivity of wheatstone bridge is maximum.
  • when the galvanometer and the cell are interchanged, then the balancing of wheat stone bridge will be effected.
  • Kirchoff's first law for the currents meeting at the Junctions in an electric circuit shows the conservation of charge.
  • Rheostat can be used as potential divider.
For the following circuit the potential difference between x and y in volt is :-
278170.png
  • 10
  • 50
  • 100
  • 0
Electromotive force of a cell is basically a 
  • force
  • power
  • work
  • current capacity
How many electrons flow per sec. through the filament of a 220 V and 110 W electric bulb :-
  • $$3.125\times 10^{18}$$
  • $$3.125\times 10^{17}$$
  • $$312.5\times 10^{18}$$
  • $$31.25\times 10^{18}$$
Figure $$(a)$$ below shows a Wheatstone bridge in which $$P, Q, R, S$$ are fixed resistances, $$G$$ is a galvanometer and $$B$$ is a battery. For this particular case the galvanometer shows zero deflection. Now, only the positions of $$B$$ and $$G$$ are interchanged,. as shown in figure $$(b)$$. The new deflection of the galvanometer.


310754.jpg
  • Is to the left.
  • Is to the right.
  • Is zero.
  • Depends on the values of $$P, Q, R, S$$.
If $$R_1$$ and $$R_2$$ are the filament resistances of a $$200 W$$ bulb and a $$100 W$$ bulb respectively designed to operate on the same voltage, then:
  • $$R_{1}= 2R_{2}$$
  • $$R_{2}= 2 R_{1}$$
  • $$R_{2}= 4R_{1}$$
  • $$R_{1}=4R_{2}$$
Which one of the following will not conduct electricity?
  • solid NaCl
  • $$CuSO_4$$ solution
  • graphite
  • acidified water
In these three circuits all the batteries are identical and have negligible internal resistance, and all the light bulbs are identical. Rank all 5 light bulbs (A, B, C, D, E) in order of brightness from brightest to dimmest.
303621.png
  • A = B = C > D = E
  • A > B = C > D = E
  • A = D = E > B = C
  • A = D = E > B > C
  • D = E > A > B = C
In the electrolysis of NaCl
  • $$Cl^-$$ is oxidised at anode
  • $$Cl^-$$ is reduced at anode
  • $$Cl^-$$ is reduced at cathode
  • $$Cl^-$$ is neither reduced nor oxidised
In the following circuit, each resistor has a resistance of $$15 \Omega$$ and the battery has an e.m.f. of $$12 V$$ with negligible internal resistance.
When a resistor of resistance $$R$$ is connected between $$D \& F$$, no current flows through the galvanometer (not shown in the figure) connected between $$C \& F$$. Calculate the value of $$R$$.


310770_39116202d660456f90ceb8dc96a86fcb.png
  • $$10 \Omega$$
  • $$15 \Omega$$
  • $$5 \Omega$$
  • $$30 \Omega$$
Two long straight cylindrical conductors with resistivities $$\rho_1$$ and $$\rho_ 2$$ respectively are joined together as shown in figure. If current I flows through the conductors, the magnitude of the total free charge at the interface of the two conductors is
292083.png
  • zero
  • $$\displaystyle \frac{(\rho_1 - \rho_2) I \varepsilon_0}{2}$$
  • $$\varepsilon_0 I |\rho_1 - \rho|$$
  • $$\varepsilon_0 I |\rho_1 + \rho|$$
An electric iron of heating element of resistance $$88 \Omega$$ is used at $$220$$ volt for $$2$$ hours. The electric energy spent, in unit, will be: 
  • $$0.8$$
  • $$1.1$$
  • $$2.2$$
  • $$8.8$$
Choose the correct option
303824.png
  • rubber rod becomes positive and fur becomes negative
  • both rod becomes positive
  • rubber rod becomes negative and fur becomes positive
  • both becomes neutral
In a battery five dry cells each of 1.5 volt have internal resistance of $$0.2, 0.3, 0.4, 0.5$$ and $$0.6\Omega $$ are present in series. The battery is connected to a $$1 \Omega$$ resistance. Identify the correct statement (s) :
  • Current in the circuit will be $$2.5 A$$
  • Current in the circuit will be $$1.5 A$$
  • On short circuiting the battery $$3.75A$$ current will flow
  • Both $$(A)$$ and $$(C)$$
The diagram shows a resistor connected to a cell of e.m.f. $$2 V$$ How much heat energy is produced in the resistor in six seconds?

314727_5c570cc4fafb4c46855033b94d92a6bc.png
  • $$2.5 J$$
  • $$4.8 J$$
  • $$10 J$$
  • $$60 J$$
Two bulbs, one of 200 W and the other of 100 W, are connected in series with a 100 V battery which has no internal resistance. Then,
330924_42fae60c99ea4911980973f182e7fbed.png
  • The current passing through the 200W bulb is more than that through the 100W bulb
  • The power dissipation in the 200W bulb is more than that In the 100 W bulb
  • The voltage drop across the 200W bulb is more than that across the 100W bulb
  • The power dissipation In the 100W bulb is more than that in the 200W bulb
On a bulb is written 220 Volt and 60 watt. Find out the resistance of the bulb and the value of the current flowing through it. 
  • 806.66 ohm 0.27 ampere
  • 500 ohm 12 ampere
  • 200 ohm 14 ampere
  • 100 ohm 11 ampere
How many electrons constitute current of one micro ampere in one second?
  • $$6.25\times10^8$$
  • $$6.25\times10^{12}$$
  • $$6.25\times10^9$$
  • $$6.25\times10^{15}$$
 what is $$i$$?
330847_f356211df13f491dbbb164e55d131e82.png
  • $$-4$$mA
  • $$+2$$mA
  • $$+4$$mA
  • $$+8$$mA
Figure below shows a portion of an electric circuit with the currents in ampere and their directions. The magnitude and direction of the current in the portion $$PQ$$ is: 
311021.jpg
  • $$0A$$
  • $$3A$$ from $$P$$ to $$Q$$
  • $$4A$$ from $$Q$$ to $$P$$
  • $$6A$$ from $$Q$$ to $$P$$
In which of the following cells, the potential difference between the terminals of a cell exceeds its emf.
318854_dbce99655cf1425eb11f58a3d04a1893.png
  • $$a$$
  • $$b$$
  • $$c$$
  • $$d$$
An electric iron draws a current of 15 A from a 220 V supply, What is the cost of using iron for 30 min everyday for 15 days if the cost of unit (1 unit =1 kWhr) is 2 rupees ? 
  • Rs 49.5
  • Rs 60
  • Rs 40
  • Rs 10
The circuit given below is for the operation of an industrial fan. The resistance of the fan is $$3 ohm$$. The regulator provided with the fan is a fixed resistor and a variable resistor in parallel. Under what value of the variable resistance given, power transferred to the fans will be maximum? The power source of the fan is a dc source with internal resistance of $$6 ohm$$

330747_20e8315631444d50ba69afdda458c367.png
  • 3 $$\Omega$$
  • $$0$$
  • $$\infty$$
  • $$6 $$$$\Omega$$
The number of joules contained in $$1  kWh$$ is
  • $$36 \times {10}^{2}$$
  • $$36 \times {10}^{3}$$
  • $$36 \times {10}^{4}$$
  • $$3.6 \times {10}^{6}$$
An electric heater has a rating of 2 kW, 220 V. The cost of running the heater for 10 hours at the rate of Rs 350 per unit is Rs ____
  • 216
  • 165
  • 209
  • 105
In the circuits shown below the ammeter $$A$$ reads $$4   amp$$ and the voltmeter $$V$$ reads $$20  volts$$. The value of the resistance $$R$$ is
359566_21a6973af5b74fb8a114bd2014890831.png
  • Slightly more than 5 ohms
  • Slightly less than 5 ohms
  • Exactly 5 ohms
  • None of the above
A source of electromotive force (emf) is a:
  • Cell
  • Battery
  • Generator
  • All of these
Calculate the resistance offered by 3 HP water pump which runs on 220 V supply
  • 21.63 $$\Omega$$
  • 42.6 $$\Omega$$
  • 63.2 $$\Omega$$
  • 37.6 $$\Omega$$
Figure below shows a portion of an electric circuit with the currents in ampreres and their directions. The magnitude and direction of the current in the portion PQ is :
334222_dca213b9920c4a5a9e5b0fd813c529a4.png
  • 0A
  • 3A from P to Q
  • 4A from Q to P
  • 6A from Q to P
0:0:1


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