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State Biot-Savarts law. Derive an expression for magnetic field at the center of a circular coil of -turns carrying current .
Ans: Biot - Savart law states that the magnetic field $\mathrm{dB}$ due to a current element dI at any point would be as following: $$ \begin{array}{l} \mathrm{dB} \propto \mathrm{dl} \\ \mathrm{dB}...
A straight wire carries a current of . An electron moving at is at distance from the wire. Find the force acting on the electron if its velocity is directed towards the wire.
Ans: We are given the current through the straight wire to be, $I=10 \mathrm{~A}$ Speed of the electron, $\mathrm{v}=10^{7} \mathrm{~m} / \mathrm{s}$ Distance of electron from the wire,...
Give one difference each between diamagnetic and ferromagnetic substances. Give one example of each.
Ans: Diamagnetic substances are the ones that are weakly repelled by a magnet. For example, gold. Ferromagnetic materials are the ones that are strongly attracted by a magnet. For example, iron.
A steady current flows in the network What will be the magnetic field at the center of the network?
Ans: The magnetic field at the center of the network is zero. This is because, magnetic field at the center of the loop would just equal and opposite $i . e .$, magnetic field due PQR is equal and...
A cyclotron is not suitable to accelerate electron. Why?
Ans: A cyclotron is not suitable to accelerate electron as its mass is known to be less due to which they gain speed and step out of the dee immediately,
Two wires of equal lengths are bent in the form of two loops. One of the loops is square shaped whereas the other loop is circular. These are suspended in a uniform magnetic field and the same current is passed through them. Which loop will experience greater torque? Give reasons.
Ans: We know the expression for torque as, $$ \begin{array}{l} \tau=\mathrm{NIAB} \\ \Rightarrow \tau \propto \mathrm{A} \end{array} $$ Since, we know that the area of circular loops is more than...
What will be the path of a charged particle moving along the direction of a uniform magnetic field?
Ans: The path of a charged particle moving along the direction of a uniform magnetic field would be a straight line path as no force would act on the particle.
State two properties of the material of the wire used for suspension of the coil in a moving coil galvanometer.
Ans: Two properties of the material of the wire used for suspension of the coil in a moving coil galvanometer are: i. Non-Brittle conductor ii. Restoring Torque per unit twist should be small.
V.I graph for a metallic wire at two different temperatures Which of these two temperatures is higher and why?
Ans: From the graph: Slope $=\frac{\mathrm{i}}{\mathrm{V}}$ It is known that, $\frac{i}{V}=\frac{1}{R}$ It means that the smaller the slope, the larger the resistance.
Two heated wires of the same dimensions are first connected in series and then it’s parallel to a source of supply. What will be the ratio of heat produced in the two cases?
Ans: It is known that, $$ \begin{array}{l} H=I^{2} R t \quad\left(I=\frac{V}{R}\right) \\ \Rightarrow H=\frac{V^{2}}{R^{2}} \times R \times t \\ \Rightarrow H=\frac{V^{2}}{R} t \\ \Rightarrow H...
Resistivities of copper, silver and manganin are and respectively which of these is the best conductor?
Ans: The resistance is directly proportional to specific resistance (resistivity), when length and area of cross-section is made constant. $R=\frac{\rho I}{A}$ Hence, silver is the best conductor as...
What is the work done in moving a point change from corner to corner of a square when a charge exists at the centre of the square?
Ans: Point $A \& B$ are at the same distance from the point $O$. Hence,