• Human body resistance is about
 a. 400 Ω b. 1000 Ω c. 20 Ω d. None of the above

Ans.       b.

• With the increase in temperature of a metallic resistor, product of its resistivity and conductivity
 a. Remains constant b. Increases c. May increase or decrease d. Decreases

Ans.       a.

• Due to drop of current by 3 %, the incandescence of lamp decreases  by
 a. 12 % b. 6 % c. 3 % d. 15 %

Ans.       b.

Hint: P = I2R

• Material used to make filament of an electric bulb is
 a. Nichrome b. Aluminium c. Copper d. Tungsten

Ans.       d.

• Specific resistance of wire depends upon
 a. Length of material b. Mass c. Area of cross-section d. None of the above

Ans.       d.

• Two electric bulbs having same voltage rating and resistance of R1 and R2 respectively have powers of 200 W and 100 W. What is the possible relationship?
 R1 = 4R2 R2 = 4R1 R2 = 2R1 R1 = 2R2

Ans.       c.

• Best conductor of electricity is
 a. Gold b. Silver c. Copper d. None of the above

Ans.       b.

• Ampere – hour is the unit of
 a. Strength of current b. Power c. Quantity of electricity d. None of the above

Ans.       c.

• The amount of current, flowing through a circuit having constant resistance, is being tripled. What is the amount of power increases?
 a. 9 times b. 3 times c. 1/3 times d. 1/9 times

Ans.       a.

• The electrons, exists in the last orbit of an atom, are called
 a. Thermionic electrons b. Valance electrons c. Free Electrons d. Bound electrons

Ans.       b.

• Resistance of a straight conductor is independent of
 a. Cross-sectional area b. Shape of cross-section c. temperature d. Material

Ans.       b.

• Function of E.M.F. in a circuit is to
 a. Maintain potential difference b. Increase circuit resistance c. Decrease circuit resistance d. None of the above

Ans.       a.

• Unit of potential difference is similar to the unit of
 a. Power b. Energy c. Charge d. None of the above

Ans.       b.

• An amount of 0.32 A current is flowing through the filament of an electric lamp over 1 hour. Calculate the number of free electrons passing through the filament in that duration.
 a. 8.5 x 1019 b. 7.2 x 1021 c. 5.6 x 1025 d. None of the above

Ans.       b.

• Conductivity is reciprocal of
 a. Resistivity b. Current density c. Resistance d. Inductance

Ans.       a.

• If two resistors having resistances Ra and Rb respectively, then choose the correct option stated about their resistivity. [Given, Ra < Rb and ρa , ρb are their resistivity respectively.]
 a. ρa < ρb b. ρa = ρb c. ρa > ρb d. Information insufficient

Ans.       d.

• Calculate the amount of voltage drop across a 1 kW electric heater, having 40 Ω resistances when the heater becomes hot.
 a. 180 V b. 220 V c. 200 V d. 230 V

Ans.       c.

• Electric current in a discharge tube containing a gas is due to
 a. Electrons and positive ions both b. Positive ions only c. Electrons and positive ions both d. Electrons only

Ans.       a.

• Wire which has very high value of conductance is known as
 a. Moderately good conductor b. Semiconductor c. Very good conductor d. None of the above

Ans.       c.

• The resistance of the coil of a heater, marked  as 2000 W, 200 V, is
 a. 20 Ω b. 0.2 Ω c. 1/10 Ω d. None of the above

Ans.       a.

• Germanium behaves as ……………. at 0 K.
 a. a superconductor b. a conductor c. a ferromagnetic substance d. an insulator

Ans.       d.

• Constantan has ………… temperature co-efficient of resistance.
 a. Positive b. Almost zero c. Negative d. Undefined

Ans.       b.

• A copper wire of resistance 10 Ω is being stretched to 1/10 th of its original length. The new resistance will be –
 a. 11 Ω b. 9.1 Ω c. 12.1 Ω d. None of the above

Ans.       c.

• In case of liquids, ohm’s law is
 a. Partially obeyed b. Not obeyed c. Fully obeyed d. None of the above

Ans.       c.

• Specific resistance of a wire depends upon its
 a. Length b. Cross-sectional area c. Material d. None of the above

Ans.       c.

• What will be the resistance of a carbon electrode at 85°C, having a resistance of 0.125 Ω at 20°C?  [Given, temperature co-efficient of carbon is -0.0005 at 20°C]
 a. 0.121 Ω b. O.53 Ω c. 1.21 Ω d. None of the above

Ans.       a.

Hint:      R85 = R20 [1 + α20  (t2 – t1)] = 0.125 [1 + (-0.0005 x 65)] = 0.121 Ω

• The value of temperature co-efficient of resistance (α) depends upon
 a. Volume of the material b. Temperature and nature of the material c. Length of the material d. Cross-sectional area of the material

Ans.      b.

• Electric current is due to the flow of
 a. Neutral particles only b. Negative charges only c. Positive charges only d. Both positive and negative charges

Ans.      d.

• Choose the correct resistance value, having color code yellow, violet, orange and silver respectively.
 a. 4.7 kΩ  20 % b. 47 kΩ  10 % c. 47 kΩ  20 % d. None of the above

Ans.      b.

Hint:     Yellow (4)  Violet (7) x Orange (103)  Silver (10 %) = 47 x 103  10 % = 47 kΩ  10 %

• A piece of Aluminium (Al) and Germanium (Ge) are moved from T1 K to T2 K. What will happen with their resistance?
 a. Resistance of Aluminium increases and that of Germanium decreases. b. Resistance of Aluminium decreases and that of Germanium increases. c. Each of them increases d. Each of them decreases

Ans.      b.

• If temperature increases, specific resistance of a Metallic conductor
 a. Remains unchanged b. Decreases c. First decreases, then increases d. Increases

Ans.      d.

• What is the value of α0  according to the above figure 1.1 ?
 a. 0.01 per °C b. 0.004 per °C c. 0.005 per °C d. 0.05 per °C

Ans.      c.

• What is the value of α50 according to the above figure 1.1 ?
 a. 0.004 per °C b. 0.5 per °C c. 0.05 per °C d. None of the above

Ans.       a.

• Insulators have ………… temperature co-efficient of resistance.
 a. Positive b. Negative c. Almost zero d. Undefined

Ans.       b.

• SI unit of conductivity is
 a. mho/m b. mho-m c. ohm/m d. ohm-m

Ans.       a.

• What is the amount of current flowing in 0.1 s, if a number of 1020 electrons pass from a point A to a point B? [Given, charge of each electron = 1.6 x  10-19 C]
 a. 160 A b. 0.16 A c. 1 A d. None of the above

Ans.       a.

• Example of non-ohmic resistance
 a. Carbon resistance b. Aluminium wire c. Tungsten wire d. Copper wire

Ans.       a.

• If the number of valance electrons of an atom is less than 4, the substance is usually
 a. An insulator b. A semiconductor c. A conductor d. None of the above
• The diameter of an atom is about
 a. 10-8  m b. 10-11 m c. 10-4 m d. 10-10 m

Ans.       d.

• Choose the best material for making connecting wires.
 a. Nichrome b.  Aluminium c. Constantan d. Copper

Ans.       d.

• Semiconductors have ………… temperature co-efficient of resistance.
 a. Positive b. Zero c. Negative d. Undefined

Ans.       a.

• An energy source provides 50 mJ of energy for every micro coulomb of charge that flows. The potential difference of the energy source is
 a. 5 kV b. 50 kV c. 50 V d. None of the above

Ans.       b.

• Mass of proton is ………. the mass of electron
 a. Less than b. Greater than c. About 1837 times d. About 627 times

Ans.       c.

• A wire of particular length has a resistance of 6 ohms. Find the resistance of another wire of same material, which has twice the cross-sectional area and three times the length.
 a. 16 ohms b. 8 ohms c. 9 ohms d. None of the above

Ans.       c.

• Ampere – second is the unit of
 a. Potential b. e.m.f. c. Charge d. Energy

Ans.       c.

• Manganin wire is used for making standard resistance because of its
 a. Negligibly small temperature coefficient of resistance b. High specific resistance c. High melting point d. Low specific resistance

Ans.       a.

• The resistance of a wire is 1 Ω at 300 K. At what temperature the resistance will be 2 Ω ? [Given that the temperature co-efficient of resistance of the wire is 0.00125 per °C.]
 a. 1100 K b. 1076 K c. 1210 K d. None of the above

Ans.       a.

• If the number of valance electrons of an atom is 4, the substance is usually
 a. An insulator b. A semiconductor c. A conductor d. None of the above

Ans.       b.

• How long does 50 µC of charge take to pass a point in a circuit, if current flow is 15 mA?
 a. 4.56 x 10-6 s b. 0.475 x 10-5 s c. 3.33 x 10-3 s d. None of the above

Ans.       c.