CBSE Questions for Class 12 Medical Physics Current Electricity Quiz 11 - MCQExams.com

In the circuit shown below, the cell is ideal, with $$emf=2V$$. The resistance of the coil of the galvanometer $$G$$ is $$1 \Omega$$. The steady current through the galvanometer is
1122489_396790a4b8414c9d9cbce9df53c447a0.jpg
  • $$0.2A$$
  • $$0.1A$$
  • $$0.4A$$
  • Zero
In an electrolyte $$3.2\times 10^{18}$$ bivalent positive ions drift to the right per second while $$3.6\times 10^{18}$$ monovalent negative ions drift to the left per second. Then the current is 
  • $$1.6$$ amp to the left
  • $$1.6$$ amp to the right
  • $$0.45$$ amp to the right
  • $$0.45$$ amp to the left
Variation of current and voltage in a conductor has been shown in the diagram below. The resistance of the conductor is.
1815238_563018952aa3455b97e8809d2c6e877d.png
  • $$4$$ ohm
  • $$2$$ ohm
  • $$3$$ ohm
  • $$1$$ ohm
Which is a wrong statement
  • The Wheatstone bridge is most sensitive when all the four resistance are of the same order
  • In a balanced Wheatstone bridge, interchanging the position of galvanometer and cell affects the balance of the bridge
  • Kirchhoff's first law (for currents meeting at a junction in a electric circuit) expresses the conversion of change
  • The rheostat can be used a a potential divider
A potential difference of $$V$$ is applied at the ends of a copper wire of length $$l$$ and sdiameter $$d$$. On doubling only $$d$$, drift velocity
  • Becomes two times
  • Becomes half
  • Does not change
  • Becomes one fourth
A solenoid is at potential of difference $$60\ V$$ and current flows through it is $$15$$ ampere, then the resistance of coil will be 
  • $$4\ \Omega$$
  • $$8\ \Omega$$
  • $$0.25\ \Omega$$
  • $$2\ \Omega$$
Consider the circuit given here with the following parameters E.M.F. of the cell $$=12\ V$$. Internal resistance of the cell $$=2\omega$$. Resistance $$R=4\Omega$$
Which one of the following statements in true 
1815279_96f505ac4a264fb7a799236891568d36.png
  • Rate of energy loss in the source is $$=8\, W$$
  • Rate of energy conversion in the source is $$16\ W$$
  • Power output in is $$=8\ W$$
  • Potential drop across $$R$$ is $$=16\ V$$
Kirchhoff $$I$$ law and $$II$$ law of current, proves the 
  • Conservation of charge and energy
  • Conservation of current and energy
  • Conservation of mass and charge
  • None of thee
There is a current of $$20$$ amperes in a copper wire of $$10^{-6}$$ square meter area of cross-section. If the number of free electrons per cubic meter is $$10^{29}$$, then the drift velocity is
  • $$125\times 10^{-3}m/sec$$
  • $$12.5\times 10^{-3}m/sec$$
  • $$1.25\times 10^{-3}m/sec$$
  • $$1.25\times 10^{-4}m/sec$$
Which of the following statement is correct
  • Liquid obey fully the ohm's law
  • Liquid obey partially the ohm's law
  • There is no relation between current and $$p.d$$ for liquids
  • None of the above
The drift velocity of free electrons in a conductor is $$'v'$$ when a current $$'i'$$ is flowing in it. If both the radius and current are doubled then drift velocity will be
  • $$v$$
  • $$\dfrac v2$$
  • $$\dfrac v4$$
  • $$\dfrac v8$$
A current $$I$$ is passing through a wire having two sections $$P$$ and $$Q$$ of uniform diameter $$d$$ and $$d/2$$ respectively. If the mean drift velocity in sections $$P$$ and $$Q$$ is denoted by $$v_P$$ and $$v_Q$$ respectively then
  • $$v_P =v_Q$$
  • $$v_P=\dfrac 12 v_Q$$
  • $$v_P=\dfrac 14 v_Q$$
  • $$v_P =2 v_Q$$
In a balanced Wheatstone's network, the resistance in the arms $$Q$$ and $$S$$ are interchanged. As a result of this
  • Network is not balanced
  • Network is still balanced
  • Galvanometer shows zero deflection
  • Galvanometer and the cell must be interchanged to balance
A copper wire has a square cross-section $$2.0\ mm$$ on a side. It carries a current of $$8\ A$$ and the density of the electrons is $$8\times 10^{28}m^{-3}$$. The drift speed of electrons is equal to 
  • $$0.156\times 10^{-3}\ m.s$$
  • $$0.156\times 10^{-2}\ m.s$$
  • $$3.12\times 10^{-3}\ m.s$$
  • $$3.12\times 10^{-2}\ m.s$$
The resistance of an incadescent lamp is
  • Greater when switched off
  • Smaller when switched on
  • Greater when switched on
  • The same whether it is switched off or switched on
If you are provided three resistances $$2 \Omega, 3 \Omega$$ and $$6 \Omega$$. How will you connect them so as to obtain the equivalent resistance of $$4\Omega$$
  • None of these
The material of wire of potentiometer is
  • Copper
  • Steel
  • Mangamint
  • Aluminum
At room temperature copper has free electrons density of $$8.4\times 10^{28}$$ per $$m^3$$. The copper conductor has a cross-section of $$10^{-6}m$$ and carries a current of $$5.4\ A$$, The electrons drift velocity in copper is
  • $$400\ m/s$$
  • $$0.4\ m/s$$
  • $$0.4\ mm/s$$
  • $$72\ m/s$$
Consider the circuit below. All bulbs are identical. Choose the CORRECT option 
1280302_5b772f39159248deab62d9f6c849b7dc.PNG
  • If the bulb A fuse,then bulb C stays lighted, bulb B bums brightly
  • If the bulb B fuse, then bulb C goes off and D stays lighted
  • If the bulb C fuse, bulbs A and B goes off
  • If the bulb d fuse, the event is unnoticable, and bulbs A,B,C, and stays lighted
Ina potentiometer experiment two cells of e.m.f and $$E$$ are used in series and in conjunction and the balancing length is found to be $$58\ cm$$ of the wire. If the polarity of $$E$$ is revered then the balancing length becomes $$29\ cm$$. The ratio $$\dfrac{E_1}{E_2}$$ of the e.m.f of the two cell is
  • $$1:1$$
  • $$2:1$$
  • $$3:1$$
  • $$4:1$$
The internal resistance of a primary cell is 4 ohm. It generates a current of 0 .2 amp in an external resistance of 21 ohm. The rate of which chemical energy is consumed providing the current is
  • $$0 . 42$$ J/s
  • $$0 . 84$$ J/s
  • $$5 $$ J/s
  • $$1$$ J/s
The resistor of resistance R is connected to 25 V supply and heat produced in it 25 J sec. The value of R is
  • $$225 \Omega $$
  • $$1 \Omega $$
  • $$25 \Omega $$
  • $$50 \Omega $$
Silver and copper voltameter are connected in parallel with a battery of e.m.f. 12 V. In 30 minutes, 1 gm of silver and 1.8 gm of copper are liberated. The power supplied by the battery is
  • 24.13 J/sec
  • 2.413 J/13
  • 0.2413 J/sec
  • 2413 J/sec
Two bulbs of $$100 W$$ and $$200 W$$ working at $$220$$ volt are joined in series with 220 volt supply. Total power consumed wll be approximately.
  • $$65$$ watt
  • $$33$$ watt
  • $$300$$ watt
  • $$100$$ watt
A $$60 \ Watt$$ bulb operates on $$220 \ V$$ supply. The current flowing through the bulb is
  • $$\dfrac{11}{3} \ amp$$ 
  • $$\dfrac{3}{11} \ amp$$ 
  • $$3 \ amp$$ 
  • $$6 \ amp$$ 
A hot electric iron has a resistance of $$80 \Omega $$ and is used on a 200 V source. The electrical energy if it is used for hours, will be
  • $$8000 Wh$$
  • $$2000 Wh$$
  • $$1000 Wh$$
  • $$800 Wh$$
In an electric heater 4 amp current passes for 1 minute at potential difference of 250 volt, the power of heater and energy consumed will be respectively
  • 1 kW, 60 kJ
  • 0.5 kW, 30 kJ
  • 10 kW, 600 kJ
  • None of thesee
If a 2 kW boiler is used everyday for  hour, then electrical energy consumed by boiler in thirty days is
  • $$15 $$ unit
  • $$60 $$ unit
  • $$120 $$ unit
  • $$240 $$ unit
For ensuring dissipation of same energy in all three resistors $$(R_{1},R_{2},R_{3})$$ connected as shown in figure, their values must be related as]
1817403_b39d17ed298c405e97d49b44b600e4db.png
  • $$R_{1}=R_{2}=R_{3}$$
  • $$R_{2}=R_{3}andR_{1}=4R_{2}$$
  • $$R_{2}=R_{3}andR_{1}=\dfrac{1}{4}R_{2}$$
  • $$R_{1}=R_{2}+R_{3}$$
An electric is designed to draw power P at voltage V.If the voltage is V it draws a power P. Then
  • $$P = \left ( \dfrac{V_{0}}{V} \right )^{2}P_{0}$$
  • $$P = \left ( \dfrac{V}{V_{0}} \right )^{2}P_{0}$$
  • $$P = \left ( \dfrac{V}{V_{0}} \right )P_{0}$$
  • $$P = \left ( \dfrac{V_{0}}{V} \right )P_{0}$$
An electric bulb marked 40 W and 200 V, is used in a circuit of supply voltage 100 v, Now its power is
  • $$100 W$$
  • $$40 W$$
  • $$20 W$$
  • $$10 W$$
If a $$5 \,V$$ battery is provoding $$2 \,A$$ current in a conductor then what is the resistance of conductor ?
  • $$3$$ Ohm
  • $$2.5$$ Ohm
  • $$10$$ Ohm
  • $$2$$ Ohm
In the figure, the potentiometer wire AB of length L and resistance $$9r$$ is joined to the cell D of emf $$\varepsilon  $$ and internal resistance r. The cell Cs emf is $$\epsilon  /2$$ and its internal resistance is $$2r$$. The galvanometer G will show no deflection when the length AJ is

41516.jpg
  • $$\dfrac{4L}{9}$$
  • $$\dfrac{5L}{9}$$
  • $$\dfrac{7L}{18}$$
  • $$\dfrac{11L}{18}$$
What happens to the current in each resistor when resistors of different values in parallel combination are connected to a source of electricity?
  • Values of current and potential difference are different
  • Values of current and potential difference are same
  • Values of current are different but value of potential difference is same
  • Values of current are the same but values of potential difference are different
Kilowatt hour is unit of
  • Energy
  • Power
  • Impulse
  • Force
Kirchhoffs first and second laws are based on
  • Charge and Energy Conservation Laws
  • Current and Energy Conservation Laws
  • Mass and Charge Conservation Laws
  • None of these
Potentiometer is a type of instrument by which potential difference can be measured
  • Zero
  • Infinite
  • Uncertain
  • Depends on external resistance
In a Wheatstone bridge, the position of battery and galvanometer is interchanged, then the new balanced position will be
  • Unchanged
  • Will changed
  • Can't say anything
  • May change or may not be, it depends upon the resistance of galvanometer and battery
Five resistances of R $$\Omega$$ were taken. First three resistances are connected in parallel combination and rest two are connected in series combination, then the equivalent resistance is :
  • $$\frac{3}{7} R \ \Omega$$
  • $$\frac{7}{3} R \ \Omega$$
  • $$\frac{7}{8} R \ \Omega$$
  • $$\frac{8}{7} R \ \Omega$$
A conducting resistance is connected to the battery and temperature of conductor decreases by the process of cooling then the value of current will be : 
  • increased
  • decreased
  • remain constant
  • zero
Kirchhoff's first law, i.e., $$\sum I = 0$$ at a junction, deals with the conservation of
  • charge
  • energy
  • momentum
  • mass
When the balance point is obtained in the potentiometer, a current is drawn from
  • both the cells and auxiliary battery
  • cell only
  • auxiliary battery only
  • neither cell nor auxiliary battery
The resistance of one conducting wire is $$10 $$. How much electric current will flow by connecting it with a battery of $$1.5 V$$ ?
  • $$0.15 mA$$
  • $$1.5 mA$$
  • $$15 mA$$
  • $$150 mA$$
The current in a metallic conductor is plotted against voltage at two
different temperatures $$T_{1}$$ and $$T_{2}$$. Which is correct

41547.jpg
  • $$T_{1}$$ > $$T_{2}$$
  • $$T_{1}$$ < $$T_{2}$$
  • $$T_{1} = T_{2}$$
  • none
In Wheat stones bridge shown in the figure, galvanometer gives no deflection on pressing the key. The balance condition for the bridge is :

12571.png
  • $$\dfrac{R_{1}}{R_{2}}=\dfrac{C_{1}}{C_{2}}$$
  • $$\dfrac{R_{1}}{R_{2}}=\dfrac{C_{2}}{C_{1}}$$
  • $$\dfrac{R_{1}}{R_{1}+R_{2}}=\dfrac{C_{1}}{C_{1}-C_{2}}$$
  • $$\dfrac{R_{1}}{R_{1}-R_{2}}=\dfrac{C_{1}}{C_{1}+C_{2}}$$
On a bulb it is written $$220\ V$$ and $$60\ W$$. Find out the resistance of the bulb and the value of the current flowing through it:
  • $$806.67\ \Omega \ \text{and} \ 0.27\ A$$
  • $$500\ \Omega \ \text{and} \ 2\ A$$
  • $$200\ \Omega \ \text{and} \ 4\ A$$
  • $$100\ \Omega \ \text{and} \ 1\ A$$
copper rod AB of length L, pivoted at one end A, rotates at constant angular velocity $$\omega $$, at right angles to a uniform magnetic field of induction B. The e.m.f developed between the mid point C of the rod and end B is
41914.jpg
  • $$\dfrac{B\omega l^{2}}{4}$$
  • $$\dfrac{B\omega l^{2}}{2}$$
  • $$\dfrac{3B\omega l^{2}}{4}$$
  • $$\dfrac{3B\omega l^{2}}{8}$$
Two non ideal batteries are connected in parallel. Consider the following statements:
The equivalent emf is smaller than either of the two emfs.
The equivalent internal resistance is smaller than either of the two internal resistances.
  • both 1 and 2 are correct
  • 1 is correct but 2 is wrong
  • 2 is correct but 1 is wrong
  • Both 1 and 2 are wrong
In the circuit shown in fig., the potential difference between the points C and D is balanced against 40 cm length of potentiometer wire of total length 100 cm. In order to balance the potential difference between the points D and E, the jockey should be pressed on potentiometer wire at a distance of

12603.JPG
  • 16 cm
  • 32 cm
  • 56 cm
  • 80 cm
A battery of emf $$E_{0}$$ $$=$$ 12 V is connected across a 4m long uniform wire having resistance 4$$\Omega $$/m. The cells of small emfs $$\varepsilon_{1} $$ $$=$$ 2V and $$\varepsilon_{2} $$ $$=$$ 4V having internal resistance 2$$\Omega $$ and 6$$\Omega $$ respectively, are connected as shown in the figure. If galvanometer shows no deflection at the point N, the distance of point N from the point A is equal to

41522_647f0a7741314af284ab27f6364b10ca.png
  • $$\dfrac{1}{6}m $$
  • $$\dfrac{1}{3}m $$
  • $$25 cm$$
  • $$50 cm$$
0:0:1


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