Two Mark Questions
1. Name the unit of (a) electrical resistance (b) resistivity
2. Define One Ohm
3. Define Resistivity
4. Determine the direction of conventional current?
5. What is electrical power? Write its unit.
Three Mark Questions
6. You take two resistors of resistance 2R and 3R and connect them in parallel in an electric circuit. Calculate the ratio of the electrical power consumed by 2R and 3R?
7. A small bulb has a resistance of 2Ω when cold. It takes up a current of 0.4 A from a source of 4V and then starts glowing. Calculate (i) the resistance of the bulb when it is glowing and
(ii) Elaborate on the reason for the difference in resistance?
8. Define resistance and resistivity and also give the relation between them. Explain the dependence of resistance on temperature.
9. A bulb is rated at 330V- 110W. What do you think is its resistance? Three such bulbs burn for 5hrs at a stretch. What is the energy consumed? Calculate the cost in rupees if the rate is 70 paise per unit?
10. Calculate the resistance of 2 km long copper wire of radius 2 mm. (Resistivity of copper = 1.72 x 1 0-8)
11. What connection is used in domestic appliances and why?
12. A 250 watt electric bulb is lighted for 5 hours daily and four 6 watt bulbs are lighted for 4.5 hours daily. Calculate the energy consumed (in kWh) in the month of February.
13. A torch bulb is rated at 3V and 600mA. Calculate it’s
(a) Power b) Resistance c) Energy consumed if it is lighted for 4 Hrs.
14. State and derive joule’s law. An electric iron consumes energy at rate of 420w when heating is at maximum rate and 180 w when heating is at minimum. The voltage is 220V .What is the current and resistant in each case?
15. A piece of wire having a resistance R is cut into five equal parts.
(i) How will the resistance of each part of the wire compare with the original resistance?
(ii) If the five parts of the wire are placed in parallel, how will the resistance of the combination compare with the resistance of the original wire? What will be ratio of resistance in series to that of parallel?
Answers
Answer:
Explanation:
1. The ohm is the SI derived unit of electrical resistance, named after German physicist Georg Ohm.
2. The ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of one volt, applied to these points, produces in the conductor a current of one ampere, the conductor not being the seat of any electromotive force.
3. Resistivity, electrical resistance of a conductor of unit cross-sectional area and unit length. ... A characteristic property of each material, resistivity is useful in comparing various materials on the basis of their ability to conduct electric currents. High resistivity designates poor conductors.
4. The direction of Conventional current or simply ,Current is from positive terminal to negative terminal means the direction of current is opposite to the direction of electron flow.
5. Electric power is the rate at which work is done or energy is transformed into an electrical circuit. Simply put, it is a measure of how much energy is used in a span of time.