Advertisements
Advertisements
प्रश्न
Find the expression for the resistivity of a material and state the SI unit of resistivity.
Advertisements
उत्तर
The resistance of a conductor is directly proportional to its length l and inversely proportional to its area of cross-section A.
`R prop l` and `R prop 1/A`
`:. R prop l/A`
`:. R = rho 1/A`
where ρ is the proportionality constant and is called the resistivity of the material of the conductor.
Rearranging the above equation,
`rho = "RA"/l`
This is the expression for resistivity.
The SI unit of resistivity is ohm-meter (Ω.m).
APPEARS IN
संबंधित प्रश्न
What will be the change in the current if the potential difference is kept constant and the resistance of the circuit is made four times?
- It will remain unchanged.
- It will become four times.
- It will become one-fourth.
- It will become half.
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
An electrical bulb is marked 200V, 100W. Calculate the electrical resistance of its filament. If five such
bulbs are connected in series to a 200V supply, how much current will flow through them?
Keeping the p.d. constant, the resistance of a circuit is halved. The current will become:
(a) one-fourth
(b) four time
(c) half
(d) double
A resistance of 40 ohms and one of 60 ohms are arranged in series across 220 volt supply. Find the heat in joules produced by this combination of resistances in half a minute.
Calculate the current flowing through a wire of resistance 5 Ω connected to a battery of potential difference 3 V.
A wire of resistance 3 ohm and length 10 cm is stretched to length 30 cm. Assuming that it has a uniform cross section, what will be its new resistance?
Rewrite the following statement by selecting the correct option.
The S.I. unit of resistance is __________.
State the relation correlating the electric current flowing in a conductor and the voltage applied across it. Also, draw a graph to show this. relationship.
State the limitations of Ohm’s law.
SI unit of resistance is:
A student carries out an experiment and plots the V-I graph of three samples of nichrome wire with resistances R1, R2 and R3 respectively. Which of the following is hue?
Assertion: The statement of Ohm’s law is K = IR.
Reason: V = IR is the equation which defines resistance.
State Ohm’s law? How can it be verified experimentally? Does it hold good under all conditions? Comment.
Calculate the total resistance of the circuit and find the total current in the circuit.
Why should an ammeter have low resistance?
The voltage - current readings of a certain material are shown in the table given below:
| Voltage (V) | 10 V | 20 V | 30 V |
| Current (I) | 2 A | 3 A | 4 A |
Study the table.
- State whether the conductor used is ohmic or non-ohmic.
- Justify your answer.
- State Ohm's law.
