Advertisements
Advertisements
Question
A given wire of resistance 1 Ω is stretched to double its length. What will be its new resistance?
Advertisements
Solution
Let ‘I’ be the length and ‘a’ be the area of cross – section
of the resistor with resistance, R = 1Ω
`"R" = ∝ l/r^2`
when the wire is stretched to double its length,
the new length I’ = 2I and the new area of cross section,
`a^1 = a/2 "and" l^1 = 2l`
`"R"^1 ∝ l^1/a^1`
∴ `"R"^1 ∝ (2l)/(a/2)`
`"R"^1 ∝ (4l)/a`
R1 ∝ 4R
Resistance increases to 4 times original resistance = R1 = 4Ω
APPEARS IN
RELATED QUESTIONS
The figure given below shows an electric circuit in which current flows from a 6 V battery through two resistors.
- Are the resistors connected in series with each other or in parallel?
- For each resistors, state the p.d. across it.
- The current flowing from the battery is shared between the two resistors. Which resistor will have bigger share of the current?
- Calculate the effective resistance of the two resistors.
- Calculate the current that flows from the battery.
Find the potential difference required to pass a current of 0.2 A in a wire of resistance 20Ω
Draw a schematic diagram of an electric circuit consisting of a battery of two cells each of 1.5 V, 5 Ω, 10 Ω and 15 Ω resistors and a plug key, all connected in series.
A wire is passed through a piece of cardboard as shown in fig .. An electric current flows vertically down the wire and then flows back up. The two sections of the write are observed to repel each other.
(a) Wi th the aid of a diagram, describe how you would plot the magnetic field lines on the card .
(b) Sketch the magnetic field patterns around both the sections of the wire. Use your sketch to explain why the two sections repel each other.
(c) The repulsive force between the two sections is small. What changes could be made to increase it?
Which part of an electrical appliance is earthed?
Water : pipe :: Electric current : ______.
When an electric current is passed, electrons move from:
