Q.1
Four wires of equal length and of resistance 5Ω each are connected in the form of a square. The equivalent resistance between the diagonally opposite corners of the square is
  • a) 5 Ω
  • b)10 Ω
  • c)20 Ω
  • d)(5/4) Ω
Q.2
The supply voltage to a room is 120V. The resistance of the lead wire is 6ohm. A 60 watt bulb is already giving light. What is the decrease in voltage across the bulb when a 240 watt heater is switched on
  • a) zero volt
  • b) 2.9 volt
  • c) 13.3 volt
  • d) 10.4 v
Q.3
A 60 watt incandescent lamp operates at 120V. The number of electrons passing through the filament per second
  • a)1..6×1012
  • b) 3.125×1018
  • c)7200
  • d)12.5 ×1018
Q.4
A wire 100 cm long and 2.0 mm diameter has a resistance of 0.7Ω. The electrical resistivity of the material is
  • a) 4.4 ×10⁻⁶ Ω × m
  • b) 2.2 ×10⁻⁶ Ω × m
  • c)1.1 ×10⁻⁶ Ω × m
  • d)0.22 ×10⁻⁶ Ω × m
Q.5
When a current I is set up in wire of radius r, the drift speed is vd. If the same current is set up through a wire of radius 2r., the drift speed will be
  • a) vd /4
  • b) vd /2
  • c)2vd
  • d)4vd
Q.6
An electron charge (e) is revolving in a circular orbit of radius r round a nucleus of charge Ze with speed v. The equivalent current is
  • a)zero
  • b) ev/2πr
  • c)Zev/2πr
  • d)e2πr/ v
Q.7
In absence of electric field, the mean velocity of free electrons in a conductor at absolute zero temperature T is
  • a) zero
  • b) independent of temperature
  • c)proportional to √T
  • d)proportional to T
Q.8
Two resistance are joined in parallel whose resultant is 6/5 Ω. One of the resistance wire is broken and the effective resistance become 2&Ω. Then the resistance in ohm of the wire that got broken was
  • a) 3/5
  • b) 2
  • c)6/5
  • d)3
Q.9
In a circuit containing two unequal resistors connected in parallel
  • a) the current is same in both the resistors
  • b) the current is large in larger resistor
  • c) voltage drop is same across both the resistors
  • d) voltage drop is larger across larger resistance
Q.10
In an electrolyte if e denotes the charge on each type of ion and n+ and n- denote the number of positive and negative ions per unit volume and V+ and V- denotes the drift velocities of positive and negative ions, then the current density is given by
  • a)en+V+
  • b) en-V-
  • c)en+V+ + en-V-
  • d)eA[n+V+ + n-V-]
Q.11
A certain piece of copper wire is to be shaped in to a conductor of minimum resistance. Its length and diameter should be
  • a) L, D
  • b) 2L, (1/2) D
  • c)(1/2) L, 2D
  • d)2L, 2D
Q.12
A square aluminum rod is 1 m long and 5mm on edge. What must be the radius of another aluminum rod whose length is 1m and which has the same resistance as previous rod
  • a) 5.0 mm
  • b) 4.2 mm
  • c) 2.8 mm
  • d) 1.4 mm
Q.13
Certain substances lose their electrical resistance at very low temperature. These substances are called
  • a) good conductors
  • b) semi-conductors
  • c) super conductors
  • d) dielectrics
Q.14
A wire of length 5 m and radius 1 mm has a resistance of 1 ohm. What length of wire of same material at the same temperature and of radius 2mm will also have same resistance of 1 ohm
  • a)1.25 m
  • b) 2.5 m
  • c)10.0 m
  • d)20.0 m
Q.15
The resistance of carbon filament at 0°C is 104ohms. It is connected in series to an iron wire. The temperature coefficient of resistivity of carbon and iron are -0.0003 and +0.0052 per °C respectively. What must be the resistance of the iron wire so that the combined resistance does not change with temperature?
  • a) 1.5 ohms
  • b) 6 ohms
  • c)1.5 ohms
  • d)156/104 ohms
Q.16
A wire has resistance 12 ohms. It is bent in the form of an equilateral triangle. The effective resistance between any two corners of triangle is
  • a) 9/4 ohms
  • b) 12 ohms
  • c)6 ohms
  • d)8/3 ohms
Q.17
The equivalent resistance of the parallel combination is
  • a) smaller than the largest resistance
  • b) larger than the largest resistance
  • c) smaller than the smallest resistance
  • d) larger than the smallest resistance
Q.18
A wire is cut into 4 pieces, which are put together side by side to obtain one conductor. If the original resistance of the wire was R, the resistance of the bundle will be
  • a) R/4
  • b) R/8
  • c)R/16
  • d)R/32
Q.19
For ohmic conductor the drift velocity vd and the electric field applied across it are related as
  • a) vd ∝ √E
  • b) vd ∝ E
  • c)vd ∝ E3/2
  • d)vd ∝ E2
Q.20
When piece of aluminum wire of finite length is drawn through a series of die 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
Q.21
The unit of electrical conductivity is
  • a)ohm/metre
  • b) ohm × metre
  • c)1/ (ohm × metre)
  • d)mho×metre
Q.22
The resistance of a wire at temperature t°C and 0°C are related as
  • a) Rt=Ro [ 1+ αt]
  • b) Rt=Ro [ 1 - αt]
  • c)Rt=Ro2 [1 + αt]
  • d)Rt=Ro2 [1 - αt]
Q.23
The resistance of straight conductor does not depend upon its
  • a) shape of cross-section
  • b) temperature
  • c)material
  • d)length
Q.24
the specific resistance of all metals is most affected by
  • a) temperature
  • b) pressure
  • c) degree of illumination
  • d) applied magnetic field
Q.25
Through a metallic conductor an electric current is due to drift of
  • a) free electrons
  • b) positive and negative ions
  • c)free electrons and holes
  • d)protons
Q.26
When there is an electric current through conducting wire along its length, then an electric field must exist
  • a) outside the wire but normal to it
  • b) outside the wire but parallel to it
  • c)inside the wire but parallel to it
  • d)inside the wire but normal to it
Q.27
Which of the following characteristics of electrons determines the current in a conductor
  • a) drift velocity alone
  • b) thermal velocity alone
  • c) both drift velocity and thermally velocity
  • d) neither drift nor thermal velocity
Q.28
through a semi-conductor, an electric current is due to drift of
  • b) free electrons and holes
  • c)positive and negative ions
  • d)protons
  • a)free electrons
Q.29
Two copper wires have their masses in the ratio 8:They have their lengths in the ratio 3:Their resistance's are in the ratio of
  • a) 4:9
  • b) 16:9
  • c)27:32
  • d)27:128
Q.30
The current-voltage variation for a wire of copper of length L and area A is shown in the figure. The slope of the line will be
ch-14_que_no-192_img_no1.png
  • a) less if the experiment is done at higher temperature
  • b) more if a wire of silver of same dimensions is used
  • c) will be doubled if the length of the wire is doubled
  • d) will be halved if the length is doubled
0 h : 0 m : 1 s