Question
Electrons are continuously in motion within a conductor but there is no current in it unless some source of potential is applied across its ends. Give reason.
✓
Answer
In the absence of any external source the motion of electrons in a conductor is random and electrons collide continuously with the positive ions of metal. This causes a random change in direction of motion. The average velocity of random motion of electrons in any direction is zero, hence current is zero.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A capacitor of capacitance $10\mu\text{F}$ is connected across a battery of emf 6.0V through a resistance of $20\text{k}\Omega$ for 4.0s. The battery is then replaced by a thick wire. What will be the charge on the capacitor 4.0s after the battery is disconnected?
→The neutron separation energy is defined as the energy required to remove a neutron from the nucleus. Obtain the neutron separation energies of the nuclei ${ }_{20}^{41} Ca$ and ${ }_{13}^{27} Al$ from the following data:
$\begin{array}{l} m \left({ }_{20}^{40} C a\right)=39.962591 u \\
m \left({ }_{20}^{41} C a\right)=40.962278 u \\
m \left({ }_{13}^{26} A l\right)=25.986895 u \\
m \left({ }_{13}^{27} A l\right)=26.981541 u \end{array}$
→$\begin{array}{l} m \left({ }_{20}^{40} C a\right)=39.962591 u \\
m \left({ }_{20}^{41} C a\right)=40.962278 u \\
m \left({ }_{13}^{26} A l\right)=25.986895 u \\
m \left({ }_{13}^{27} A l\right)=26.981541 u \end{array}$
Write the expression for the force on a charge moving in a magnetic field.
Use this expression to define the SI unit of magnetic field.
A partially plane polarised beam of light is passed through a Polaroid. Show graphically the variation of the transmitted light intensity with angle of rotation of the Polaroid.
- In Young's double slit experiment, two slits are 1 mm apart, and the screen is placed 1 m away from the slits. Calculate the fringe width when light of wavelength 500 nm is used.
- What should be the width of each slit in order to obtain 10 maxima of the double slits pattern within the central maximum of the single slit pattern?
A small pin fixed on a table top is viewed from above a distance of 50 cm. By what distance would the pin appear to be raised if it is viewed from the same point through a 15 cm thick glass slab held parallel to the table? Refractive index of glass = 1.5. Does the answer depend on the location of the slab?
A cubical box of volume 216cm3 is made up of 0.1cm thick wood. The inside is heated electrically by a 100W heater. It is found that the temperature difference between the inside and the outside surface is 5°C in steady state. Assuming that the entire electrical energy spent appears as heat, find the thermal conductivity of the material of the box.
What are isotopes? Explain with an example how the average mass can be obtained from the relative proportions of different isotopes of the same element.
Calculate the energy that can be obtained from 1kg of water through the fusion reaction
2H + 2H → 3H + p.
Assume that 1.5 × 10-2% of natural water is heavy water D2O (by number of molecules) and all the deuterium is used for fusion.
2H + 2H → 3H + p.
Assume that 1.5 × 10-2% of natural water is heavy water D2O (by number of molecules) and all the deuterium is used for fusion.
Find the total energy stored in the capacitors in the given network.
