- What is the value of equivalent resistance if 50 Resistors of 5 ohm resistance are connected in Series (a) 10 Ohm (b) 50 Ohm (c) 250 Ohm (d) 500 Ohm
- The heating element of an electric heater should be made of a material that should have: (a) low specific resistance and low melting point. (b) high specific resistance and high melting point. (c) high specific resistance and low melting point. (d) low specific resistance and high melting point.
- The specific resistance (Resistivity) of a wire (a) Will depend on its length (b)Will depend on its radius (c) Will depend on the type of material of the wire (d) Will depend on none of the above
- Electrical energy is measured in (a) Watt (b) Horse power (c) Kilowatt (d)Kilowatt-hour
- A fuse is placed in series with the circuit to protect against (a) High power (b) High voltage (c) High current (d) Over heating
- The direction of flow of current through electric circuit is (a) From low potential to high potential (b) From high potential to low potential (c)Does not depends upon the potential value (d) Current cannot floe through circuit
- Equivalent resistance of the given circuit in ohm is- (a) 9 (b) 2 (c) 7 (d) 4.5
- Assertion (A) : The metals and alloys are good conductors of electricity.
Reason (R) : Bronze is an alloy of copper and tin and it is not a good conductor of electricity.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true - Assertion (A) : Alloys are commonly used in electrical heating devices like electric iron and heater.
Reason (R): Resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points then their constituent metals.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true. - If a person has five resistors each of value 1/5 Ω, then the maximum resistance he can obtain by connecting them is (a) 1 Ω (b) 5 Ω (c) 10 Ω (d) 25 Ω
Subjective Question Practice
- State and explain Ohm’s law. Define resistance and give its SI unit. What is meant by 1 ohm resistance? Draw V-I graph for an ohmic conductor and list its two important features (5 Marks)
- A V-I graph for a nichrome wire is given below. What do you infer from this graph? Draw a labelled circuit diagram to obtain such a graph (3 Marks)
- Calculate the resistance of a metal wire of length 2m and area of cross section 1.55 × 106 m², if the resistivity of the metal be 2.8 × 10-8 Ωm. (2 Marks)
- List the factors on which the resistance of a conductor in the shape of a wire depends.
- Why are metals good conductors of electricity whereas glass is a bad conductor of electricity ? Give reason.
- Why are alloys commonly used in electrical heating devices ? Give reason. ( 3Marks)
- A copper wire has diameter 0.5 mm and resistivity 1.6 × 10-8 Ω m. Calculate the length of this wire to make it resistance 100 Ω. How much does the resistance change if the diameter is doubled without changing its length? (3 Marks)
- If the radius of a current carrying conductor is halved, how does current through it change? (2 Marks)
- Three resistors of 10 Ω, 15 Ω and 5 Ω are connected in parallel. Find their equivalent resistance. (2 Marks)