Advertisements
Advertisements
प्रश्न
Define the term resistivity.
Advertisements
उत्तर
The resistivity of a material is the resistance of a wire of that material of unit length and unit area of cross-section.
संबंधित प्रश्न
Three 2 V cells are connected in series and used as a battery in a circuit.
- What is the p.d. at the terminals of the battery?
- How many joules of electrical energy does 1 C gain on passing through
- one cell
- all three cells?
What is an electric current?
A student made an electric circuit shown here to measure the current through two lamps.
Are the lamps in series or parallel?
(a) Are the lamps in series or parallel?
(b) The student has made a mistake in this circuit. What is the mistake?
(c) Draw a circuit diagram to show the correct way to connect the circuit. Use the proper circuit symbols in your diagram.
A 5 V battery is connected to two 20 Ω resistors which are joined together in series.
(a) Draw a circuit diagram to represent this. Add an arrow to indicate the direction of conventional current flow in the circuit.
(b) What is the effective resistance of the two resistors?
(c) Calculate the current that flows from the battery?
(d) What is the p.d. across each resistor?
Ten bulbs are connected in a series circuit to a power supply line. Ten identical bulbs are connected in a parallel circuit to an identical power supply line.
- Which circuit would have the highest voltage across each bulb?
- In which circuit would the bulbs be brighter?
- In which circuit, if one bulb blows out, all others will stop glowing?
- Which circuit would have less current in it?
Consider the circuit given below when A, B and C are three identical light bulbs of constant resistance. 
(a) List the bulbs in order of increasing brightness.
(b) If C burns out, what will be the brightness of A now compared with before?
(c) If B burns out instead, what will be the brightness of A and C compared with before?
How do you think the brightness of two lamps arranged in parallel compares with the brightness of two lamps arranged in series (both arrangements having one cell)?
In which of the following cases more electrical energy is consumed per hour?
(i) A current of 1 ampere passed through a resistance of 300 ohms.
(ii) A current of 2 amperes passed through a resistance of 100 ohms.
An electric bulb is rated as 10 W, 220 V. How many of these bulbs can be connected in parallel across the two wires of 220 V supply line if the maximum current which can be drawn is 5 A?
Name two effects produced by electric current.
Find the potential difference required to pass a current of 0.2 A in a wire of resistance 20Ω
The following circuit diagram shows three resistors 2 Ω, 4 Ω and R Ω connected to a battery of e.m.f 2V and internal resistance 3 Ω. If the main current of 0.25 A flows through the circuit, find:
- the p.d. across the 4 Ω resistors,
- the p.d. across the internal resistance of the cell,
- the p.d. across the R Ω or 2 Ω resistors, and
- the value of R.
The work done in moving unit positive charge across two points in an electric circuit is a measure of
What is international convention of colour coding in a cable?
Define the following:
Electromotive force
If the potential differences between two parts of a thundercloud is 10s V,
what is the amount of energy given up during the passage of 20 coulombs?
(a)2x10-7J
(b)200J
(c)Sx106 j
(d)2x 109J
(e)2x 1010 J
In fig. XY is at right angles to the magnetic field. The direction in which XY should be moved to induce an electron flow in the direction Y to X as indicated by the arrow is:
Answer the following question.
An electric lamp of resistance 20 Ω and a conductor of resistance 4 0 are connected to a 6 V battery as shown in the circuit. Calculate: 
(a) the total resistance of the circuit,
(b) the current through the circuit,
(c) the potential difference across the (i) electric lamp and (ii) conductor, and
(d) power of the lamp.
Answer the following question.
What is the function of a galvanometer in a circuit?
State the conditions for the flow of charge in a circuit from one point to the other.
Three resistances, of which two are equal when connected in series have an effective resistance of 30 ohms. When the three resistances are connected in parallel, the effective resistances is 3 ohms. Find the values of the individual resistances.
MCB is used to protect household electrical appliances.
Match the following:
| 1. | 1 mA | a. | series |
| 2. | 1 pA | b. | ohmmeter |
| 3. | Ammeter | c. | 10-6 ampere |
| 4. | Electrical resistivity | d. | 10-3 ampere |
For current to flow, one needs art open circuit.
What is the rate at which charges flow past a point on a circuit?
In metallic conductors, the charge carriers responsible for producing electric current are:
In the process of current flow through a conductor, the amount of charge passing per unit time gives:
