CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 4 - MCQExams.com

In a potentiometer wire experiment the emf of a battery in the primary circuit is 20V and its
internal resistance is 5$$\Omega $$. There is a resistance box in series with the battery and the potentiometer
wire, whose resistance can be varied from 120$$\Omega $$ to 170$$\Omega $$. The resistance of the potentiometer wire is 75$$\Omega $$. Find the potential differences using a potentiometer.
  • 5V
  • 6V
  • 7.5V
  • 8V
A potentiometer circuit is set up as shown. The potential gradient across the potentiometer wire is k volt/cm and the ammeter, present in the circuit, reads 1.0 A when two way key is switched off. The balance points, when the key between the terminals (i) 1 and 2 (ii) 1 and 3, is plugged in, are found to be at lengths $$l_{1}$$cm and $$l_{2}$$ cm respectively. The magnitudes, of the resistors R and X, in ohms, are then, equal respectively to:
68644.jpg
  • $$k(l_{2}-l_{1})$$ and $$kl_{2}$$
  • $$kl_{1}$$ and $$k(l_{2}-l_{1})$$
  • $$k(l_{2}-l_{1})$$ and $$kl_{1}$$
  • $$kl_{1}$$ and $$kl_{2}$$
n identical cells are joined in series with its two cells A and B in the loop with reversed polarities.
EMF of each shell is E and internal resistance r. Potential difference across cell A or B is:
  • $$\dfrac{2E}{n}$$
  • $$2E|1-\dfrac{1}{n}|$$
  • $$\dfrac{4E}{n}$$
  • $$2E|1-\dfrac{2}{n}|$$
Which of the following statement is true regarding the Kirchoffs laws?
  • The junction rule is a statement of conservation of energy and the loop rule is a statement of conservation of charge
  • The junction rule as well as the loop rule are statements of conservation of charge.
  • The junction rule as well as the loop rule are statements of conservation of energy.
  • The junction rule is a statement of conservation of charge and the loop rule is a statement of conservation of energy.
The resistance of a metal increases with the increase of temperature due to :
  • Number of electrons
  • Velocity of electrons
  • Scattering of electrons with core ions
  • Thermal motion of core ions
Observe the figure given below.
Find the current passing through $$6\Omega$$ resistor.

84511_7c503e3093074e8ea56938a6589bb146.png
  • 0.72 A
  • 0.80 A
  • 0.48 A
  • Cannot be said
Kilowatt-hour is the unit of :
  • potential difference.
  • electric power.
  • electrical energy.
  • charge.
  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
  • Assertion is correct but Reason is incorrect
  • Assertion is incorrect but Reason is correct
You have a large supply of light bulbs and a battery. You start with one light bulb connected to the battery and notice its brightness. You then add one light bulb at a time, each new bulb being added in series to the previous bulbs then
  • Brightness of the bulbs will increase
  • Current through the bulbs will increase
  • Power transferred from the battery will decrease
  • Lifetime of the battery will decrease
Find the currents $$I_1$$ and $$I_2$$ for the circuit shown in given figure.

82311.png
  • $$I_1=-6 A$$ and $$I_2=9 A$$
  • $$I_1=6 A$$ and $$I_2=9 A$$
  • $$I_1=-6 A$$ and $$I_2=-9 A$$
  • $$I_1=-9 A$$ and $$I_2=6 A$$
$$1kWh= $$ _________?
  • $$3600000\ J$$
  • $$10000\ J$$
  • $$4.2\ J$$
  • $$25000\ J$$
Kilowatt is the unit of electrical _______ but kilowatt-hour is the unit of electrical _______.
  • Power, Energy
  • Power, Electric potential
  • Power, Current
  • Energy, Power
What is one unit of household electrical energy in J?
  • $$1000\ J$$
  • $$3600\ J$$
  • $$0.6 \times 10^3 J$$
  • $$3.6 \times 10^6 J$$
A negatively charged rod is brought close to two metal spheres which are in contact with each other, and the spheres are separated in the presence of the rod. Then
  • The sphere close to the rod acquires a negative charge and the other sphere acquires a positive charge
  • The sphere close to the rod acquires a positive charge and the other sphere acquires a negative charge
  • Both the spheres will acquire positive charge
  • Both the spheres will acquire negative charge
Two non-ideal batteries are connected in series. Consider the following statements:
(A) The equivalent emf is larger than either of the two emfs.
(B) The equivalent internal resistance is smaller than either of the two internal resistances
  • Each of A and B is correct
  • A is correct but B is wrong
  • B is correct but A is wrong
  • Each of A and B is wrong
Every atom makes one free electron in copper. If $$1.1$$ ampere current is flowing in the wire of copper having $$1$$ mm diameter, then the drift velocity (approx.) will be (Density of copper = $$9 \times 10^3\, kg m^{-3}$$ and atomic weight = $$63$$) 
  • $$0.1$$ mm/s
  • $$0.2$$ mm/s
  • $$0.3$$ mm/s
  • $$2$$ mm/s
The value of current $$i$$ in the given circuit is:
100093_29668253510f444089ea298a2d24545f.png
  • Zero
  • 5 Amp.
  • 7 Amp.
  • 11 Amp.
When sphere C is brought in contact with the first sphere then find the charge left on sphere A and sphere C respectively.
  • $$6.5\times 10^-7C, 0C$$
  • $$3.25\times 10^{-7}C, 3.25\times 10^{-7}C$$
  • $$3.25\times 10^{-7}C, 6.5\times 10^{-7}C$$
  • $$0C, 6.5\times 10^{-7}C$$
The arm PQ can revolve with uniform speed continuously about P round the circular uniform potentiometer track XYZ. The voltage between RS will vary with respect to time :
100317_6de5fc31e21846a2a8beecabb7b5e743.png
  • Sinusoidally
  • Linearly
  • Rectangularly
  • Like saw tooth
There is a fixed potential difference between the two ends of a potentiometer. Two cells are connected in series in such a way that in one arrangement they help each other where as in the second arrangement they oppose each other. The balance point for these two combinations is obtained at 120 cm and 60 cm length respectively. The ratio of the emf of the cell is:
  • 2 :1
  • 3 :1
  • 1 : 1
  • 4: 1
If a resistance $$5\Omega $$ is connected in the left gap of a meter bridge and $$15\Omega $$ in the other gap then position of balancing point is
  • 10 cm
  • 20 cm
  • 25 cm
  • 75 cm
1 kWh $$=$$ 
  • $$36 \times 10^6$$ watt-second
  • $$36 \times 10^5$$ watt-second
  • $$36 \times 10^7$$ watt-second
  • $$36 \times 10^8$$ watt-second
A current of $$3\ A$$ flows through a resistance when it is connected across a 12V source. What should the current be if the resistance is increased by $$4\ \Omega$$ and connected across the same voltage source?
  • $$1.5\ A$$
  • 4 A
  • 1.6 A
  • 24 A
Which one of the following is different from the others?
  • Joule
  • Kilowatt hour
  • Erg
  • Watt
The given figure shows a network of currents. The current $$i$$ is
119059.jpg
  • 23 A
  • 22 A
  • 20 A
  • 25 A
To measure a small resistance $$\sim 10^{-5}\Omega$$, one should used
  • Wheatstone bridge
  • Postoffice box
  • Wein's bridge
  • Carrey Foster bridge
Which device is used to measure the potential difference between two points of a conductor in the laboratory?
  • Voltameter
  • Ammeter
  • Potentiometer
  • Galvanometer
In a potentiometer wire experiment, the emf of a battery in the primary circuit is $$20V$$ and its internal resistance is $$5\space\Omega$$. There is a resistance box in series with the battery and the potentiometer wire, whose resistance can be varied from $$120\space\Omega$$ to $$170\space\Omega$$. Resistance of the potentiometer wire is $$75\space\Omega$$. The following potential differences can be measured using this potentiometer
  • $$5V$$
  • $$6V$$
  • $$7V$$
  • $$8V$$
Three voltmeters, all having different resistances, are  joined as shown. When some potential difference is applied across A and B, their readings are $$V_1, V_2, V_3$$

152014.png
  • $$V_1=V_2$$
  • $$V_1\neq V_2$$
  • $$V_1+V_2=V_3$$
  • $$V_1+V_2 > V_3$$
A brass disc and a carbon disc of same radius are assembled alternatively to make a cylindrical conductor. The resistance of the cylinder is independent of the temperature. The ratio of thickness of the brass disc to that of the carbon disc is $$\underline{\hspace{0.5in}}$$ .$$\alpha$$ is temperature coefficient of resistance & Neglect linear expansion
  • $$\displaystyle\frac{\alpha_C\rho_C}{\alpha_B\rho_B}$$
  • $$\displaystyle\frac{\alpha_C\rho_B}{\alpha_B\rho_C}$$
  • $$\displaystyle\frac{\alpha_B\rho_C}{\alpha_C\rho_B}$$
  • $$\displaystyle\frac{\alpha_B\rho_B}{\alpha_C\rho_C}$$
Calculate the value of current $$I_2$$ in the section of networks shown in figure.
119953.jpg
  • 13 A
  • 7 A
  • 10 A
  • 3 A
Calculate the value of current $$I_4$$  in the section of networks shown in figure.
119953.jpg
  • 13 A
  • 7 A
  • 10 A
  • 3 A
In a balanced wheat stone bridge, current in the galvanometer is zero. It remains zero when
$$[1]$$. battery emf is increased
$$[2]$$. all resistances are increased by 10 ohms
$$[3]$$. all resistances are made five times
$$[4]$$. the battery and the galvanometer are interchanged
  • only $$[1]$$ is correct
  • $$[1], [2]$$ and $$[3]$$ are correct
  • $$[1], [3]$$ and $$[4]$$ are correct
  • $$[1]$$ and $$[3]$$ are correct
Three ammeters A, B and C of resistances $$R_A, R_B$$ and $$R_C$$ respectively are joined as shown. When some potential difference is applied across the terminals $$T_1$$ and $$T_2$$, their readings are $$I_A, I_B$$ and $$I_C$$ respectively

152021_a946e71f8c384442b88feda3e212cf1e.png
  • $$I_A=I_B$$
  • $$I_AR_A+I_BR_B=I_CR_C$$
  • $$\frac {I_A}{I_C}=\frac {R_C}{R_A}$$
  • $$\frac {I_B}{I_C}=\frac {R_C}{R_A+R_B}$$
Calculate the value of current $$I_3$$  in the section of networks shown in figure.
119957_597bf9799cce4b8da1a413ab3e5dad5b.png
  • 13 A
  • 7 A
  • 10 A
  • 3 A
Two cells of same emf are connected in series. Their internal resistances are $$r_1$$ and $$r_2$$ respectively and $$r_1 > r_2$$. When this combination is connected to an external resistance R then the potential difference between the terminals of first cell becomes zero. In this condition the value of R will bw
  • $$\frac {r_1-r_2}{2}$$
  • $$\frac {r_1+r_2}{2}$$
  • $$r_1-r_2$$
  • $$r_1+r_2$$
In an experiment of Wheatstone bridge, if the positions of cells and galvanometer are interchanged, then the balance points will
  • change
  • remain unchanged
  • depend on the internal resistance of the cell and resistance of the galvanometer
  • none of these
The reading of the ammeter is:
1501573_c82d0ca49dfb4fee938a375a0656d2ff.png
  • $$\dfrac { 1 }{ 8 }\ A$$
  • $$\dfrac { 3 }{ 4 }\ A$$
  • $$\dfrac { 1 }{ 2 } \ A$$
  • $$2\ A$$
Consider the following two statements:
(A) Kirchhoff's Junction Law follows from conservation of charge.
(B) Kirchhoff's Loop Law follows from conservative nature of electric field.
  • Both A and B are correct
  • A is correct but B is wrong
  • A is correct but A is wrong
  • Both A and B are wrong
Which of the following statements is/are correct for potentiometer circuit?
  • Sensitivity doesn't depend on the length of the potentiometer wire.
  • Sensitivity is inversely proportional to potential difference applied across the potentiometer wire.
  • Accuracy of potentiometer can be increased, only by increasing length of the wire.
  • Range is independent of potential difference applied across the potentiometer wire.
If I current is flowing in a potentiometer wire of length $$L$$ and resistance $$R$$, then potential gradient will be
  • $$\dfrac {IR}{L}$$
  • $$IRL$$
  • $$\dfrac {RL}{I}$$
  • $$\dfrac {IL}{R}$$
What is the current I for the circuit shown in the figure?

153461.png
  • $$3A$$
  • $$1A$$
  • $$-5A$$
  • $$5A$$
A $$ 1^{\circ}C$$ rise in temperature is observed in a conductor by passing a certain current. If the current is doubled, then the rise in temperature is approximately
  • $$2.5^{\circ}C$$
  • $$4^{\circ}C$$
  • $$2^{\circ}C$$
  • $$1^{\circ}C$$
What is the p.d. across the terminals $$(V_T)$$ of a cell with emf E  for open circuit ?
  • $$V_T< E$$
  • $$V_T>E$$
  • $$V_T=0$$
  • $$V_T=E$$
Choose the correct option.
  • $$kW=$$ unit of power and $$kWh =$$ unit of energy.
  • $$kW=$$unit of energy and $$kWh =$$ unit of power.
  • $$kW$$ and $$kWh$$ are both of unit of energy.
  • $$kW$$ and $$kWh$$ are both of unit of power.
A cell of e.m.f. $$\varepsilon$$ and internal resistance r is used to send current to an external resistance R. The total resistance of circuit,
  • $$\dfrac{Rr}{(R+r)}$$
  • $$\dfrac{R+r}{2}$$
  • $$Rr$$
  • $$R+r$$
Two resistors of resistance $$4\, \Omega$$ and $$6\, \Omega$$ are connected in parallel to a cell to draw $$0.5 A$$ current from the cell. What  is the current through resistor $$6\, \Omega$$?
  • $$0.2 \ A$$
  • $$0.5 \ A$$
  • $$2.4 \ A$$
  • $$1.2 \ A$$
The power supplied by the battery will be :
  • 15 W
  • 24 W
  • 3.6 W
  • 20 W
In an experiment of verification of Ohm's law, following observations are obtained:
Potential difference V (in volt)0.51.01.52.02.5
Current I (in ampere)0.20.40.60.81.0
What will be the potential difference V when the current I is 0.5 A ?
  • $$1.25 V.$$
  • $$0.5 V$$
  • $$2 V$$
  • $$1 V$$
The e.m.f. of the cell is
  • $$1.2 V$$
  • $$4.8 V$$
  • $$1.8 V$$
  • $$2 V$$
0:0:1


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