CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 3 - MCQExams.com

SI unit of electrical energy is
  • Joule
  • Kilowatt hour
  • KiloJoule
  • Watt hour
When does two elements are said to be in series?
  • When same current physically flows through both elements
  • When different current physically flows through both elements
  • When no current physically flows through both elements
  • None of these
Electromotive Force (EMF) may be defined as:
  • work done per coulomb on the charge.
  • drift velocity of electrons.
  • flow of electron.
  • the number of coulombs of charge per second.
Consider the following two statements:
1) Kirchoff's junction law follows from the conservation of charge
2) Kirchoff's loop law follows from the conservation of energy. 
Which of the following is correct?
  • both 1 and 2 are wrong
  • 1 is correct and 2 is wrong
  • 1 is wrong and 2 is correct
  • both 1 and 2 are correct
Which of the following is not a correct statement with respect to the given circuit?
591609.png
  • Switch $$S$$ is closed
  • Current is flowing in the circuit
  • $$B$$ and $$C$$ are connected in series
  • $$A$$ is connected in series to $$B$$ and $$C$$
Your are given three equal resistances. In how many combinations can they be arranged?
  • Three
  • Four
  • Five
  • Two
Which of the following component is connected in parallel in the circuit?
591599.png
  • Rheostat
  • Capacitor
  • Bulb
  • LED
Which of the following methods does not help to minimize the error due to contact resistance in Wheatstone's meter bridge experiment:
  • The wire used must be uniform
  • The wire used must be non-uniform
  • Null point is obtained near the middle of the wire
  • Interchange the positions of unknown resistance (X) and known resistance(R)
For a metallic wire, the ratio $$\displaystyle \frac{V}{i}$$ (where, V = applied potential difference and i = current flowing)
  • is independent of temperature
  • increases as the temperature rises
  • decreases as the temperature rises
  • increases or decreases as temperature rises depending upon the metal.
Kirchhoff's law of junction, $$\displaystyle \sum { I } =0$$, is based on
  • Conservation of energy
  • Conservation of charge
  • Conservation of energy as well as charge
  • Conservation of momentum
 Potentiometer measures potential more accurately because
  • it measures potential in the open circuit .
  • it uses sensitive galvanometer for null deflection .
  • it uses high resistance potentiometer wire .
  • it measures potential in the closed circuit .
A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantities constant along the length of the conductor is /are
  • current , electric current and drift velocity
  • drift speed only
  • current and drift speed only
  • current only
Which of the following statements are true?
  • During electrolysis, charge flows through electrolytic solution via electrons
  • The randomly moving electrons in a metal wire will start moving in a particular direction when a potential difference is applied across it
  • A negatively charged particle has higher electric potential than a positively charged particle
  • Charge flows only through negative charge carriers like electrons
State whether given statement is True or False
In conductors, the innermost electrons are free to move :
  • True
  • False
What happens when negative terminal of cell is connected to other negative terminal of cell in a particular circuit?
  • Current will not flow in circuit
  • Current will flow in circuit
  • temperature of cell will increase
  • cell gets damaged
Kirchoff's junction law is equivalent to ___________.
  • Conservation of energy
  • Conservation of charge
  • Conservation of electric potential
  • Conservation of electric flux
Materials that allow electrons to flow through them are known as
  • Insulator
  • Conductors
  • Electrolytes
  • Bases
State whether given statement is True or False
The wire of potentiometer is made up of Aluminium.
  • True
  • False
Why is electrical wiring usually made from copper?
  • Because copper is shiny.
  • Because copper conducts electricity.
  • Because copper is not magnetic
  • none of these
Which of the following has negative temperature coefficient of resistance?
  • Copper
  • Aluminium
  • Iron
  • Germanium
A potentiometer can be used to measure
  • emf of newly desined cell
  • internal resistance of a cell
  • unknown resistance
  • potential difference across a resistor
Identify the correct way to connect cells to make battery.
  • None of the above
If the length of potentiometer wire is increased, then the length of the previously obtained balance point will
  • Increase
  • Decrease
  • Remains unchanged
  • Becomes two times
The value of $$I$$ in the figure shown below is
638057_e289083fc0d445f58cc6f89d79f72bc1.png
  • $$19 A$$
  • $$21 A$$
  • $$8 A$$
  • $$4 A$$
A cell of emf $$6\ V$$ and resistance $$0.5\ ohm$$ is short circuited. The current in the cell is 
  • $$3\ amp$$
  • $$12\ amp$$
  • $$24\ amp$$
  • $$6\ amp$$
The current in a car headlamp is $$3.0$$A when connected to a $$12$$V battery. What is the resistance of the lamp when it is lit?
  • $$0.25\Omega$$
  • $$4.0\Omega$$
  • $$15\Omega$$
  • $$36\Omega$$
Write true or false for the following statements :
Electric power is also called BOTU. 
  • True
  • False
The given circuit is part of a certain circuit. The current through resistors are shown. The potential difference $$V_P-V_Q$$ is
1503291_9b6edd1a67904fda982b9f7b70ed406d.png
  • $$-2V$$
  • $$19V$$
  • $$22V$$
  • $$-19V$$
The Kirchhoff's first law ($$\sum$$i=0) and second law ($$\sum$$iR=$$\sum$$E) , where the symbols have their usual meanings, are respectively based on :
  • Conservation of charge, conservation of momentum
  • Conservation of energy, conservation of charge
  • Conservation of momentum, conservation of charge
  • Conservation of charge, conservation of energy
A wire has a diameter of $$0.2  mm$$ and a length of $$50  cm$$. The specific resistance of it's material is $$40\times 10^{-6}$$$$ohm  cm$$. The current through it, when a potential difference of $$2  V$$ is applied across it, is
  • $$3.14 A$$
  • $$31.4 A$$
  • $$0.314 A$$
  • $$0.0314 A$$
In a potentiometer whose wir   e resistance is 10$$\Omega $$ the potential fall per cm is V volts. To reduce it to V/4  Volt cm$$^{-1}$$, the resistance that must be connected in series with the potentiometer wire is
  • 40$$\Omega $$
  • 30$$\Omega $$
  • 20$$\Omega $$
  • 10$$\Omega $$
The resistance of a wire is 5 ohm at $$50^{\circ}$$C and 6 ohm at $$100^{\circ}$$C. The resistance of the wire at $$0^{\circ}$$C will be:
  • 2 ohm
  • 1 ohm
  • 4 ohm
  • 3 ohm
A carbon filament has resistance of 120$$\Omega $$ at $$0^{0}C$$. The resistance of a copper filament connected in series with carbon so that the combination has same resistance at all temperatures must be
$$\alpha $$ of carbon $$= -7\times 10^{-4}/^{0}C$$; $$\alpha $$ of copper $$=4\times 10^{-3}/^{0}C$$
  • 120$$\Omega $$
  • 21$$\Omega $$
  • 60$$\Omega $$
  • 210$$\Omega $$
$$n$$ identical cells, each of internal resistance $$(r)$$ are first connected in parallel and then connected in series across a resistance $$( R)$$. If the current through $$R$$ is same in both the cases then: 
  • $$R = r/2$$
  • $$r = R/2$$
  • $$R = r$$
  • $$r = 0$$
Assertion : The equivalent resistance between the points X and Y in the figure is 10.
Reason : According to Wheatstone bridge, points A and C have the same potential.

424.jpg
  • Both (A) and (R) are true and (R) is the correct explanation of A
  • Both (A) and (R) are true but (R) is not the correct explanation of A
  • (A) is true but (R) is false
  • (A) is false but (R) is true
The resistance of a bulb filament is 100$$\Omega $$ at a temperature of 100$$^{0}$$C. If its temperature coefficient of resistance be 0.005 per $$^{0}$$C , its resistance will become 200$$\Omega $$ at a temperature of :
  • 300$$^{0}$$C
  • 400$$^{0}$$C
  • 500$$^{0}$$C
  • 200$$^{0}$$C
In a potentiometer of ten wires, the balance point is obtained on the sixth wire. To shift the balance point to eighth wire, we should
  • increase resistance in the primary circuit.
  • decrease resistance in the primary circuit.
  • decrease resistance in series with the cell whose e.m.f. has to be measured.
  • increase resistance in series with the cell whose e.m.f. has to be measure.
A potentiometer wire 10 m long has a resistance of 40$$\Omega$$. It is connected in series with a resistance box and a 2V storage cell. If the potential gradient along the wire is 0.1 mV/cm ,  the resistance in the box is
  • 760$$\Omega $$
  • 260$$\Omega$$
  • 1060$$\Omega$$
  • 960$$\Omega$$
The current that passes through 20 ohm resistance when it is connected in parallel with a 30 ohm resistance and this set is connected to a battery of 2V is
  • 0.2A
  • 0.3A
  • 0.1A
  • 0.016A
The temperature coefficient resistivity of a material is $$0.0004/K$$. When the temperature of the material is increased by $$50^{o}C$$, its resistivity increases by $$2\times 10^{-8}\ ohm-meter$$.The initial resistivity of the material of the resistance
  • $$50\times 10^{-8}$$
  • $$90\times 10^{-8}$$
  • $$100\times 10^{-8}$$
  • $$200\times 10^{-8}$$
The potentiometer is more appropriate for measuring potential difference than a voltmeter because
  • the resistance of voltmeter is high
  • the sensitivity of a potentiometer is higher than that of voltmeter
  • the resistance of potentiometer wire is very low
  • the potentiometer does not draw any current from the unknown source of emf
Resistance of a resistor at temperature $$t^{0}C$$ is $$R_{t}=R_{0}(1+\alpha t+\beta t^{2})$$. Here $$R_{0}$$ is the resistance at $$0^{0}C$$. The temperature coefficient of resistance at temperature $$t^{0}C$$ is
  • $$\dfrac{(1+\alpha t+\beta t^{2})}{\alpha +2\beta t}$$
  • $$\alpha +2\beta t$$
  • $$\dfrac{\alpha +2\beta t}{(1+\alpha t+\beta t^{2})}$$
  • $$\dfrac{\alpha +2\beta t}{2(1+\alpha t+\beta t^{2})}$$
Four conductors of resistance 4, 3, 9 and 6 ohm are connected in AB,BC, CD and DA arms of a Wheatstone bridge. The bridge can be balanced by connecting.
  • 1) 6 ohm in series with 3 ohm conductor
  • 2) 4 ohm in parallel with 6 ohm conductor
  • 3) 3 ohm in series with 3 ohm conductor
  • 4) 5 ohm in series with 6 ohm conductor
Aluminium$$\left ( \alpha =4\times 10^{-3}K^{-1} \right )$$  resistance of 60$$\Omega $$ and carbon $$\left ( \alpha =0.5\times 10^{-3}K^{-1} \right )$$ resistance 40$$\Omega $$ are connected in parallel. The combination is heated. The effective resistance is
  • Greater than 24$$\Omega $$
  • Less than 24$$\Omega $$
  • Greater than 40$$\Omega $$
  • Greater than 100$$\Omega $$
If in a Wheatstone bridge the battery and Galvanometer are interchanged, the condition for balance
  • is disturbed
  • is not disturbed
  • depends on the internal resistance of the bridge
  • depends on the values of the resistances in the bridge
The resistance of a metallic conductor increases with temperature due to:
  • change in carrier density
  • change in dimension of the conductor
  • increase in the number of collisions among the carriers
  • increase in the rate of collisions between the carriers and the vibrating atoms of the conductor.
Consider a thin square sheet of side $$L$$ and thickness $$t$$, made of a material of resistivity $$\rho $$. The resistance between two opposite faces, shown by the shaded areas in the figure is____
42336.PNG
  • directly proportional to L
  • directly proportional to t
  • independent of L
  • independent of t
Consider a long conductor, the middle of which is earthed. If the potential difference across the two ends of the conductor is $$220\ V$$, then what is the potential at the ends and the middle point?
  • $$220\ V$$ all over the conductor
  • $$110\ V$$ and $$-110\ V$$ at ends and $$0\ V$$ at the mid point
  • $$0\ V$$ at ends and $$220\ V$$ at midpoint
  • $$-220\ V$$ all over the conductor
The length of a potentiometer wire is l. A cell of emf E is balanced at a length L/3 from the
positive end of the wire. If the length of the wire is increased by L/At what distance will the
same cell give a balance point.
  • $$\dfrac{2L}{3} $$
  • $$\dfrac{L}{2} $$
  • $$\dfrac{L}{6} $$
  • $$\dfrac{4L}{3} $$
A wheel having mass m has charges $$+q$$ and $$q$$ on diametrically opposite points. It remains in equilibrium on a rough inclined plane in the presence of uniform vertical electric field E $$=$$


41401.jpg
  • $$\dfrac{\mu g}{q}$$
  • $$\dfrac{\mu g}{2q}$$
  • $$\dfrac{\mu g\tan\theta }{2q}$$
  • None of these
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