Two wires of the same material are given. The first wire is twice as long as the second and has twice the diameter of the second. The resistance of the first will be
A
Twice of the second
B
Half of the second
C
Equal to the second
D
Four times of the second
Easy
Download our app for free and get started
B
Half of the second
b (b) By $R = \rho l/A$
Download our app
and get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
In the circuit shown, the reading of the Ammeter is doubled after the switch is closed. Each resistor has a resistance $1\,\Omega$ and the ideal cell has an $e.m.f.$ $10\,V$. Then, the Ammeter has a coil resistance equal to ............ $\Omega$
Two wires $A$ and $B$ of same material and mass have their lengths in the ratio $1 : 2$. On connecting them to the same source, the rate of heat dissipation in $B$ is found to be $5\,W$. The rate of heat dissipation in $A$ is............ $W$
Consider a metallic cube of edge length $L$. Its resistance, $R$, measured across its opposite faces is $R =\frac{ m _{ e } v }{ ne ^2 L ^2}$, where $n$ is the number density and $v$ is the drift speed of electrons in the cube, and $e$ and $m _{ e }$ are the charge and mass of an electron respectively. Assuming the de-Broglie wavelength of the electron to be $L$, the maximum resistance of the sample is closest to ............. $\,\Omega$ $\left(e=1.60 \times 10^{-19} \,C ; m _{ e }=9.11 \times 10^{-31} \,kg\right.$; Planck's constant, $h=6.63 \times 10^{-34} \,Js$ )
Two wires of same length and thickness having specific resistances $6\, \Omega \,cm$ and $3 \,\Omega\, cm$ respectively are connected in parallel. The effective resistivity is $\rho\, \Omega \,cm$. The value of $\rho$ to the nearest integer, is ..... .
Four resistances are connected in a circuit in the given figure. The electric current flowing through $4\, ohm$ and $6\, ohm$ resistance is respectively