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

A cell of e.m.f. ε and internal resistance r sends current 1.0A when it is connected to an external resistance 1.9Ω. But it sends current 0.5A when it is connected to an external resistance 3.9Ω. Calculate the values of ε and r.
  • ε=2.0V,r=0.1Ω
  • ε=.1V,r=2.0Ω
  • ε=.2V,r=1.0Ω
  • 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 Ω
  • 56 Ω
  • 15 Ω
  • 13 Ω
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.Ω and 3.9Ω respectively. Neglecting any thermal expansion, find the temperature at which resistances of bolh are equal. 
αcu=4.0×103K1. and αfe=4.0×103K1.
  • 65oC
  • 75oC
  • 270oC
  • 95oC
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 T1 and T2 are shown in the figure. It is concluded that :

201003_f2a16de9d43b4910899b70024dac9e0e.png
  • T1>T2
  • T1<T2
  • T1=T2
  • T1=2T2
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 10Ω. 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 EN=1.5rN 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=10Ω,B=5Ω,C=4Ω and D=4Ω for the bridge to be balanced :-

279138.png
  • 10Ω should be connected in parallel A
  • 10Ω should be connected in series with A
  • 5Ω should be connected in series with B
  • 5Ω should be connected in parallel with B
At what temperature will the resistance of a copper wire become three times its value at 0C [Temperature coefficient of resistance for copper =4×103perC] :-
  • 400C
  • 450C
  • 500C
  • 550C
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 :-
  • 3.125×1018
  • 3.125×1017
  • 312.5×1018
  • 31.25×1018
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 R1 and R2 are the filament resistances of a 200W bulb and a 100W bulb respectively designed to operate on the same voltage, then:
  • R1=2R2
  • R2=2R1
  • R2=4R1
  • R1=4R2
Which one of the following will not conduct electricity?
  • solid NaCl
  • CuSO4 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 15Ω and the battery has an e.m.f. of 12V 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
  • 10Ω
  • 15Ω
  • 5Ω
  • 30Ω
Two long straight cylindrical conductors with resistivities ρ1 and ρ2 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
  • (ρ1ρ2)Iε02
  • ε0I|ρ1ρ|
  • ε0I|ρ1+ρ|
An electric iron of heating element of resistance 88Ω 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 0.6Ω are present in series. The battery is connected to a 1Ω resistance. Identify the correct statement (s) :
  • Current in the circuit will be 2.5A
  • Current in the circuit will be 1.5A
  • 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. 2V How much heat energy is produced in the resistor in six seconds?

314727_5c570cc4fafb4c46855033b94d92a6bc.png
  • 2.5J
  • 4.8J
  • 10J
  • 60J
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?
  • 6.25×108
  • 6.25×1012
  • 6.25×109
  • 6.25×1015
 what is i?
330847_f356211df13f491dbbb164e55d131e82.png
  • 4mA
  • +2mA
  • +4mA
  • +8mA
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 3ohm. 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 6ohm

330747_20e8315631444d50ba69afdda458c367.png
  • 3 Ω
  • 0
  • 6Ω
The number of joules contained in 1kWh is
  • 36×102
  • 36×103
  • 36×104
  • 3.6×106
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 4amp and the voltmeter V reads 20volts. 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 Ω
  • 42.6 Ω
  • 63.2 Ω
  • 37.6 Ω
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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