CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 1 - MCQExams.com

If the length of a potentiometer wire is increased by keeping constant potential difference across the wire, then _______.
  • null point is obtained at larger distance
  • there is no change in the null point
  • potential gradient is increased
  • null point is obtained at shorter distance
Charge supplied by the battery is?
  • $$120$$ pC
  • $$100$$ pC
  • $$60$$ pC
  • $$50$$ pC
When battery and galvanometer are interchanged in the case of Wheatstone bridge, then?
  • If the bride was in adjustment before interchange, it will not be in adjustment after interchange
  • If the bridge was in adjustment before interchange, it will be in adjustment after interchange
  • If the bridge was in adjustment before interchange, it may or may not be in adjustment after interchange
  • All the above
Direction of induced e.m.f. is determined by -
  • Fleming's left hand rule
  • Fleming's right hand rule
  • Maxwell' s rule
  • Ampere's rule of swimming
Metals are good conductors because:
  • outer electrons are strongly bound to the atom
  • outer electrons are loosely bound to the atom
  • inner electrons are loosely bound to the atom
  • protons can detach from the nucleus and conduct electricity
In the given circuit, no cur rent is passing through the galvanometer. If the cross-sectional diameter of AB is doubled then for null point of galvanometer the value of AC would

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  • $$x$$
  • $$x/2$$
  • $$2X$$
  • None
Calculate ratio of $${ i }_{ 1 }$$ and $$({ i }_{ 1 }+\quad { i }_{ 2 })$$.
1305639_d9cd92959b8d4ce0affa68a1aff30299.PNG
  • $$\dfrac { 4 }{ 3 } $$
  • $$\dfrac { 4 }{ 9 } $$
  • $$\dfrac { 2 }{ 5 } $$
  • zero
Two copper conductors A,B carrying currents of $$1A$$ and $$1.2A$$ respectively. If the radii are in the ratio of $$2:3$$ then the drift speed of the electrons in the two conductors are in the ratio 
  • $$5:8$$
  • $$8:15$$
  • $$15:8$$
  • $$8:5$$
The amount of work done by the cell on a unit positive charge carrier to force it to go to the point of higher potential is called
  • power
  • voltage
  • emf
  • energy
e.m.f. is measured in
  • $$\text{Joules}$$
  • $$\dfrac{\text{Joules}}{\text{coulomb}}$$
  • $$\text{Joule-coulombs}$$
  • $$\dfrac{\text{coulomb}}{\text{Joules}}$$
The emf of a cell is:
  • the potential difference across its terminals
  • the potential difference across its terminal when no current is passing through it
  • the heat produced when the cell is connected across a one ohm resistance
  • the total work done per coulomb of electricity take in a circuit in which the cell is connected
If a wire is stretched to make it $$0.1\%$$ longer, its resistance will 
  • increase by $$0.05\%$$
  • increase by $$0.2\%$$
  • decrease by $$0.2\%$$
  • decrease by $$0.05\%$$.
The resistance of wire is 5 ohm at 50C and 6 ohm at 100C. The resistance of the wire at 0C willbe
  • 2 ohm
  • 1 ohm
  • 4 ohm
  • 3 ohm
In the circuit shown, a four-wire potentiometer is made of a $$400 cm$$ long wire, which extends between A and B. The resistance per unit length of the potentiometer wire is $$r = 0.01 \Omega/cm$$. If an ideal voltmeter is connected as shown with jockey J at 50 cm from end A, the expected  reading of the voltmeter will be :-
1613751_6f79359d83d94257a5d2b0a40767509a.png
  • $$0.20 V$$
  • $$0.25 V$$
  • $$0.75 V$$
  • $$0.50 V$$
On interchanging the resistances, the balance point of a meter bridge shifts to the left by $$10$$cm. The resistance of their series combination is $$1k\Omega$$. How much was the resistance on the left slot before interchanging the resistances?
  • $$550 \Omega$$
  • $$910 \Omega$$
  • $$990 \Omega$$
  • $$505 \Omega$$

The length of a wire of a potentiometer is 100 cm, and the e.m.f. of its stand and cell is $$\mathrm{E}$$ volt. lt is employed to measure the e.m.f. of a battery whose internal resistance is 0.5 $$\Omega$$. lf the balance point is obtained at $$l=30$$ cm from the positive end, the e.m.f. of the battery is
  • $$\displaystyle \frac{30\mathrm{E}}{100.5}$$
  • $$\displaystyle \frac{30\mathrm{E}}{100-0.5}$$
  • $$\displaystyle \frac{30(\mathrm{E}-0.5\mathrm{i})}{100}$$, where i is the current in the potentiometer wire.
  • $$\displaystyle \frac{30\mathrm{E}}{100}$$
A piece of copper and another of germanium are cooled from room temperature to 77 K, the resistance of : 
  • each of them increases
  • each of them decreases
  • copper decreases and germanium increases
  • copper increases and germanium decreases
A potentiometer PQ is set up to compare two resistance as shown in the figure. The ammeter A in the circuit reads 1.0 A when two way key $$K_3$$ is open. The balance point is at a length $$l_1$$ cm from P when two way key $$K_3$$ is plugged between 2 and 1, while the balance point is at a length $$l_2$$ cm from P when key $$K_3$$ is plugged between 3 andThe ratio of two resistances $$\frac{R_1}{R_2}$$ , is found to be 
629595_d55059b89e6a40fdb6f0289cb57088d2.png
  • $$\frac{l_1}{l_1 + l_2}$$
  • $$\frac{l_1} {l_1 - l_2}$$
  • $$\frac{l_1}{l_2 - l_1}$$
  • $$\frac{l_2}{l_2 - l_1}$$
In a Wheatstone's bridge, there resistances $$\mathrm{P},\ O$$ and $$\mathrm{R}$$ connected in the three arms and the fourth arm is formed by two resistances $$\mathrm{S}_{1}$$ and $$\mathrm{S}_{2}$$ connected in parallel. The condition for bridge to be balanced will be   
  • $$\displaystyle \dfrac{\mathrm{P}}{\mathrm{O}}=\dfrac{\mathrm{R}}{\mathrm{S}_{1}+\mathrm{S}_{2}}$$
  • $$\displaystyle \dfrac{\mathrm{P}}{\mathrm{O}}=\dfrac{2\mathrm{R}}{\mathrm{S}_{1}+\mathrm{S}_{2}}$$
  • $$\displaystyle \dfrac{\mathrm{P}}{\mathrm{O}}=\dfrac{\mathrm{R}(\mathrm{S}_{1}+\mathrm{S}_{2})}{\mathrm{S}_{1}\mathrm{S}_{2}}$$
  • $$\displaystyle \dfrac{\mathrm{P}}{\mathrm{O}}=\dfrac{\mathrm{R}(\mathrm{S}_{1}+\mathrm{S}_{2})}{2\mathrm{S}_{1}\mathrm{S}_{2}}$$
A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F. because the method involves:
  • A combination of cells, galvanometer and resistances
  • Cells
  • Potential gradients
  • A condition of no current flow through the galvanometer
Kirchoffs law of junctions is also called the law of conservation of:
  • Energy
  • Charge
  • Momentum
  • Angular momentum
In comparing e.m.f.s of 2 cells with the help of potentiometer, at the balance point, the current flowing through the wire is taken from:
  • 1) Any one of these cells
  • 2) both of these cells
  • 3) Battery in the main circuit
  • 4) From an unknown source
The potential gradients on the potentiometer wire are$$V_{1}$$ and $$V_{2}$$ with an ideal cell and a real cell of same emf in the primary circuit then
  • $$V_{1}=V_{2}$$
  • $$V_{1} > V_{2}$$
  • $$V_{1} < V_{2}$$
  • $$V_{1} \leq V_{2}$$
A steady current is passing through a linear conductor of non uniform cross-section.  The net quantity of charge crossing any cross section per second is
  • Independent of area of cross-section
  • Directly proportional to the length of the conductor
  • Directly proportional to the area of cross section.
  • Inversely proportional to the length of the conductor
An electric bulb works on $$230\ V$$ line and draws $$0.1\ A$$ current. The resistance of the filament is:
  • $$230\ \Omega $$
  • $$2300\ \Omega $$
  • $$23\ \Omega $$
  • $$2.3\ \Omega $$
Assertion(A) : The e.m.f of the cell in secondary circuit must be less than e.m.f of cell in primary circuit in potentiometer.
Reason (R): Balancing length cannot be more than length of potentiometer wire.
  • Both A & R are true and R is the correct explanation of A
  • Both A & R are true and R is not a correct explanation of A
  • A is true but R is false
  • A is false but R is true
Choose the correct statement:
  • The potential difference between the terminals of a cell in closed circuit is called EMF of the cell.
  • Electromotive force and accelerating force have the same dimensions.
  • The internal resistance of an ideal cell is infinity.
  • The difference between the emf of a cell and potential difference across the ends of the cell is called lost volts.
The sensitivity of a potentiometer can be increased by
a) increasing the series resistance in the primary circuit
b) decreasing the length of the potentiometer wire
c) using a thin and high resistivity wire as a potentiometer wire
d) increasing the length of the wire
  • a and c are correct
  • b and d are correct
  • b and c are correct
  • a and d are correct
Wheatstones’s bridge cannot be used for measurement of very _______ resistances.
  • high
  • low
  • low(or) high
  • zero
Which one of the following is not the unit of energy?
  • joule
  • newton metre
  • kilowatt
  • kilowatt hour
In a meter bridge, a standard resistor of R ohm is connected in the left gap and two wires A and B are connected one after the other in the right gap. The balancing length measured from the left is 50 cm for either of them. If the two wires are connected is series and put in the right gap, the balancing length measured from the left would be (in cm)
  • 25
  • 33.3
  • 66.7
  • 75
Unit of e.m.f. of a cell is 
  • dyne
  • volt
  • ampere
  • joule
Electric current is to be passed from one body to another. For this purpose the two bodies must be joined by
  • cotton thread
  • plastic string
  • copper wire
  • rubber band
In comparing e.m.f. of two cells with the help of a potentiometer, at the balance point, the current flowing through the wire is taken from
  • one of these cells
  • both of these cells
  • the battery in the main circuit
  • none of these
The resistance of a metallic conductor :
  • Increases with rise in temperature
  • Decreases with rise in temperature
  • Remains unchanged with change in temperature
  • Becomes zero at very high temperature
Electromotive force of a battery represents
  • force
  • energy
  • electric potential energy per unit charge
  • current
State whether True or False
It is possible that a battery has some constant value of emf but the potential difference between the plates is zero.
  • True
  • False
What steady current can be drawn from an accumulator of capacity $$80\ Ah$$?
  • $$4\ A$$ for $$20\ hrs$$
  • $$40\ A$$ for $$6\ hrs$$
  • $$20\ A$$ for $$5\ hrs$$
  • $$2\ A$$ for $$100\ hrs$$
Which physical quantity cannot be determined with the help of potentiometer?
  • I
  • V
  • L
  • R
When the potential difference between two points is 1 volt and current through it is 1 A, then the resistance between the points is:
  • $$3 \, \Omega$$
  • $$2 \, \Omega$$
  • $$0.5 \, \Omega$$
  • $$1 \, \Omega$$
Which of the following quantities do not change when a resistor connected to a battery is heated due to the current?
  • Drift speed
  • Resistivity
  • Resistance
  • Number of free electrons
Electrical charge can be transferred from a charged object to another through :
  • Vacuum
  • Air
  • Insulators
  • Conductors
Name the material used for making the connection wires.
  • tin
  • copper
  • lead
  • tungsten
As the temperature of a conductor increases, its resistivity and conductivity change. The ratio of resistivity to conductivity
  • increases
  • decreases
  • remains constant
  • may increase or decrease depending on the actual temperature
The commercial unit of electric energy is $$kilowatt-hour\ (kW h)$$, commonly known as:
  • $$Unit$$
  • $$Faraday$$
  • $$Curie$$
  • None of these
A charged conductor has charge on its
  • outside surface
  • surrounding
  • middle point
  • inner surface
In the absence of an electric field, the mean velocity of free electrons in a conductor at absolute temperature $$(T)$$ is
  • $$zero$$
  • independent of $$T$$
  • proportional to $$T$$
  • proportional to $$T^2$$
Kirchoff's first law, i.e., $$\sum    i = 0$$ at a junction, deals with the conservation of
  • charge
  • energy
  • momentum
  • angular momentum
State whether true or false:
Electric charges leak rapidly from the painted edges of a conductor.
  • True
  • False
At temperature $$0 K,$$  the germanium behaves as a/an
  • conductor
  • insulator
  • super-conductor
  • ferromagnetic
0:0:1


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