- 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.
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