A current of $2\,A$ flows through a wire of crosssectional area $25.0\,mm ^2$. The number of free electrons in a cubic meter are $2.0 \times 10^{28}$. The drift velocity of the electrons is $...............\times 10^{-6}\,ms ^{-1}$ (given, charge on electron $=1.6 \times 10^{-19}\,C$ )
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The resistance of platinum wire at $0^{\circ}\,C$ is $2\,\Omega$ and $6.8\,\Omega$ at $80^{\circ} \,C$. The temperature coefficient of resistance of the wire is :
Figure shows a simple potentiometer circuit for measuring a small $e.m.f$. produced by a thermocouple. The meter wire $PQ$ has a resistance $5 \,\Omega$ and the driver cell has an e.m.f. of $2\, V$. If a balance point is obtained $0.600\, m$ along $PQ$ when measuring an e.m.f. of $6.00\, mV$, what is the value of resistance $R$ ............... $\Omega$
Two batteries one of the $\mathrm{emf}$ $3\,V$, internal resistance $1$ ohm and the other of $\mathrm{emf}$ $15\, V$, internal resistance $2$ $\mathrm{ohm}$ are connected in series with a resistance $R$ as shown. If the potential difference between $a$ and $b$ is zero the resistance of $R$ in $\mathrm{ohm}$ is
A piece of fuse wire melts when a current of $15\, ampere$ flows through it. With this current, if it dissipates $22.5\, W$, the resistance of fuse wire will be .............. $\Omega$
A null point is found at $200\,cm$ in potentiometer when cell in secondary circuit is shunted by $5\,\Omega$. When a resistance of $15\,\Omega$ is used for shunting null point moves to $300\,cm$. The internal resistance of the cell is $..............\,\Omega$.
The series combination of two batteries, both of the same emf $10 \mathrm{\;V},$ but different internal resistance of $20\; \Omega$ and $5\; \Omega,$ is connected to the parallel combination of two resistors $30\; \Omega$ and $\mathrm{R}\; \Omega .$ The voltage difference across the battery of internal resistance $20\; \Omega$ is zero, the value of $\mathrm{R}(\text { in } \Omega)$ is
At what temperature will the resistance of a copper wire become three times its value at $0\,^oC$ ................. $^oC$ (Temperature coefficient of resistance for copper = $4 × 10^{-3} \,per\, \,^oC$ )
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, $h=6.63 \times 10^{-34} \,Js$ )
The current flowing through a conductor connected across a source is $2\,A$ and $1.2\,A$ at $0^{\circ}\,C$ and $100^{\circ}\,C$ respectively. The current flowing through the conductor at $50^{\circ}\,C$ will be $......\times 10^2\,mA$.