Physics M.C.Q (1 Marks)

An electric wire is connected across a cell of e.m.f. E. The current  I is measured by an ammeter of resistance R. According to ohm's law

(a)

(b) E = IR

(c) E = R/I

(d) E = I/R

The positive temperature coefficient of resistance is for

(a) Carbon

(b) Germanium

(c) Copper

(d) An electrolyte

The resistivity of a wire

(a) Increases with the length of the wire

(b) Decreases with the area of cross-section

(c) Decreases with the length and increases with the cross-section of wire

(d) None of the above statement is correct

A wire of length 5 m and radius 1 mm has a resistance of 1 ohm. What length of the wire of the same material at the same temperature and of radius 2 mm will also have a resistance of 1 ohm

(a) 1.25 m

(b) 2.5 m

(c) 10 m

(d) 20 m

A wire is broken in four equal parts. A packet is formed by keeping the four wires together. The resistance of the packet in comparison to the resistance of the wire will be

(a) Equal

(b) One fourth

(c) One eight

(d)

A certain wire has a resistance R. The resistance of another wire identical with the first except having twice its diameter is

(a)  2R

(b) 0.25 R

(c) 4R

(d) 0.5 R

A wire 100 cm long and 2.0 mm diameter has a resistance of 0.7 ohm, the electrical resistivity of the material is

(a) 4.4	(b) 2.2
(c) 1.1	(d) 0.22

When a piece of aluminium wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become

(a) Two times

(b) Four times

(c) Eight times

(d) Sixteen times

A piece of wire of resistance 4 ohms is bent through 180°  at its mid point and the two halves are twisted together, then the resistance is

(a) 8 ohms

(b) 1 ohm

(c) 2 ohms

(d) 5 ohms

62.5  electrons per second are flowing through a wire of area of cross-section 0.1, the value of current flowing will be

(a) 1 A

(b) 0.1 A

(c) 10 A

(d) 0.11 A

The specific resistance of a wire is ρ, its volume is 3  and its resistance is 3 ohms, then its length will be

(a)

(b)

(c)

(d)

In a conductor 4 coulombs of charge flows for 2 seconds. The value of electric current will be

(a) 4 volts

(b) 4 amperes

(c) 2 amperes

(d) 2 volts

When the current i is flowing through a conductor, the drift velocity is v. If  2i  current is flowed through the same metal but having double the area of cross-section, then the drift velocity will be

(a) v/4

(b) v/2

(c) v

(d) 4v

When current flows through a conductor, then the order of drift velocity of electrons will be

(a)

(b)

(c)

(d)

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   and atomic weight = 63)

(a) 0.3 mm/sec

(b) 0.1 mm/sec

(c) 0.2 mm/sec

(d) 0.2 mm/sec

Which one is not the correct statement

(a) 1 volt × 1 coulomb = 1 joule	(b) 1 volt × 1 ampere = 1 joule/second
(c) 1 volt × 1 watt = 1 H.P.	(d) Watt-hour can be expressed in eV

On increasing the temperature of a conductor, its resistance increases because

(a) Relaxation time decreases	(b) Mass of the electrons increases
(c) Electron density decreases	(d) None of the above

If a 0.1 % increase in length due to stretching, the percentage increase in its resistance will be

(a) 0.2 %

(b) 2 %

(c) 1 %

(d) 0.1 %

The specific resistance of manganin is . The resistance of a cube of length 50 cm  will be

(a)

(b) 2.5

(c)

(d) 5

The temperature coefficient of resistance for a wire is 0.00125/℃. At 300K its resistance is 1 ohm. The temperature at which the resistance becomes 2 ohm is

(a) 1154 K

(b) 1100 K

(c) 1400 K

(d) 1127 K

When the length and area of cross-section both are doubled, then its resistance

(a) Will become half	(b) Will be doubled
(c) Will remain the same	(d) Will become four times

Two wires of the same material and equal length are joined in parallel combination.  If one of them has half the thickness of the other and the thinner wire has a resistance of 8 ohms, the resistance of the combination is equal to

(a)

(b)

(c)

(d)

To draw maximum current from a combination of cells, how should the cells be grouped

(a) Series

(b)Parallel

(c) Mixed

(d) Depends upon the relative values of external and internal resistance

The resistance of a wire is 20 ohms. It is so stretched that the length becomes three times, then the new resistance of the wire will be

(a) 6.67 ohms

(b) 60.0 ohms

(c) 120 ohms

(d) 180.0 ohms

Ohm's law is true

(a) For metallic conductors at low temperature

(b) For metallic conductors at high temperature

(c) For electrolytes when current passes through them

(d) For diode when current flows

The resistivity of iron is 1 . The resistance of a iron wire of particular length and thickness is 1 ohm. If the length and the diameter of wire both are doubled, then the resistivity in ohm - m  will be

(a)

(b) 2

(c) 4

(d) 8

The example for non-ohmic resistance is

(a) Copper wire

(b) Carbon resistance

(c) Diode

(d) Tungston wire

A current of 1 mA is flowing through a copper wire.  How many electrons will pass a given point in one second [e = 1.6 × 10^–19 Coulomb]

(a) 6.25 ×

(b) 6.25 ×

(c) 6.25 ×

(d) 6.25 ×

Drift velocity  varies with the intensity of electric field as per the relation

(a)

(b)

(c)  constant

(d)

A potentiometer wire of length 1 m and resistance 10 W is connected in series with a cell of emf 2V with internal resistance 1 W and a resistance box including a resistance R.  If potential difference between the ends of the wire is 1 mV, the value of R is

(a) 20000 W

(b) 19989 W

(c) 10000 W

(d) 9989 W

The equivalent resistance of the following diagram A and B is

(a)

(b) 9 W

(c) 6 W

(d) None of these

Assertion  :   The electric bulbs glows immediately when switch is on.

Reason      : The drift velocity of electrons in a metallic wire is very high.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Assertion  :   The temperature coefficient of resistance is positive for metals and negative for p-type semiconductor.

Reason      : The effective charge carriers in metals are negatively charged whereas in p-type semiconductor they are positively charged.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Assertion   :   In the following circuit emf is 2V and internal resistance of the cell is 1 W and R = 1W, then reading of the voltmeter is 1V.

Reason      :  V = E - ir where E = 2V, i =  and R = 1 W

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Assertion  :  There is no current in the metals in the absence of electric field.

Reason      : Motion of free electron are randomly.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

In an experiment, a graph was plotted of the potential difference V between the terminals of a cell against the circuit current i by varying load rheostat. Internal conductance of the cell is given by

(a) xy

(b)

(c)

(d) (x – y)

A battery consists of a variable number 'n' of identical cells having internal resistances connected in series. The terminals of battery are short circuited and the current i is measured. Which of the graph below shows the relation ship between i and n

(a)

(b)

(c)

(d)

A wire of resistor R is bent into a circular ring of radius r. Equivalent resistance between two points X and Y on its circumference, when angle XOY is a, can be given by

(a)

(b)

(c) R (2 p – a)

(d)

A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10 divisions per milliampere and voltage sensitivity is 2 divisions per millivolt. In order that each division reads 1 volt, the resistance in ohms needed to be connected in series with the coil will be

(a) 99995

(b) 9995

(c)

(d)

The resistance of the series combination of two resistance is S. When they are joined in parallel the total resistance is P. If S = nP, then the minimum possible value of n is

(a) 4

(b) 3

(c) 2

(d) 1

Following figure shows cross-sections through three long conductors of the same length and material, with square cross-section of edge lengths as shown. Conductor B will fit snugly within conductor A, and conductor C will fit snugly within conductor B. Relationship between their end to end resistance is

(a) RA = RB = RC	(b) RA > RB > RC
(c) RA < RB < R	(d) Information is not sufficient

12 cells each having same emf are connected in series with some cells wrongly connected. The arrangement is connected in series with an ammeter and two cells which are in series. Current is 3 A when cells and battery aid each other and is 2 A when cells and battery oppose each other. The number of cells wrongly connected is

(a) 4

(b) 1

(c) 3

(d) 2

Length of a hollow tube is 5m, it’s outer diameter is 10 cm and thickness of it’s wall is 5 mm. If resistivity of the material of the tube is 1.7 ×  W × m then resistance of tube will be

(a) 5.6 × 10–5 W

(b) 2 × 10–5 W

(c) 4 × 10–5 W

(d) None of these

In the circuit shown here, the readings of the ammeter and voltmeter are

(a) 6 A, 60 V

(b) 0.6 A, 6 V

(c) 6/11 A, 60/11 V

(d) 11/6 A, 11/60 V

A battery of internal resistance 4W is connected to the network of resistances as shown. In order to give the maximum power to the network, the value of R (in Ω) should be

(a) 4/9

(b) 8/9

(c) 2

(d) 18

Two wires of resistance R₁ and R₂ have temperature coefficient of resistance  and , respectively.  These are joined in series.  The effective temperature coefficient of resistance is

(a)

(b)

(c)

(d)

The resistance of a wire of iron is 10 ohms and temp. coefficient of resistivity is  5 . At  20 it carries 30 milliamperes of current. Keeping constant potential difference between its ends, the temperature of the wire is raised to 120. The current in milliamperes that flows in the wire is

(a) 20

(b) 15

(c) 10

(d) 40

In the shown arrangement of the experiment of the meter bridge if AC corresponding to null deflection of galvanometer is x, what would be its value if the radius of the wire AB is doubled

(a) x

(b) x/4

(c) 4x

(d) 2x

A group of N cells whose emf varies directly with the internal resistance as per the equation E_N = 1.5 r_N are connected as shown in the figure below.  The current I in the circuit is

(a) 0.51 amp

(b) 5.1 amp

(c) 0.15 amp

(d) 1.5 amp

The current in a conductor varies with time t as  where I is in ampere and t in seconds.  Electric charge flowing through a section of the conductor during t = 2 sec to t = 3 sec is

(a) 10 C

(b) 24 C

(c) 33 C

(d) 44 C