Important questions based on NCERT syllabus for Chapter 12 - Electricity:
Question-1: Define current. Is it a scalar quantity or a vector quantity? What is meant by the conventional direction of current?
Solution: 1. Rate of flow of charge with respect to time is called current.
2. It is a scalar quantity.
3. Conventional current is defined as moving in the same direction as the positive charge flow. So, in metals where the charge carriers (electrons) are negative, conventional current is in the opposite direction as the electrons.
Question-2: Define specific resistance. What is its SI unit.
Solution: 1. Electrical resistivity (also known as resistivity, specific electrical resistance, or volume resistivity) quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge.
2. Resistivity is commonly represented by the Greek letter ρ (rho). The SI unit of electrical resistivity is the ohm⋅ metre (Ω⋅m)
Question-3: Why do we use tungsten filament in bulb or lamps?
Solution: Tungsten has a high melting point (3380∘C) and becomes incandescent (i.e., emits light at a high temperature) at 2400 K.
Because of very high melting point tungsten doesn't melt. That's why in bulb or lamps we use tungsten filament.