Question
Define current density. State its unit.
✓
Answer
Magnitude of current flowing in the perpendicular direction of unit area of cross-section is known as current density J.
Current density $J =\frac{ i }{\Delta S }$, where, $\Delta S$ is area of cross-section.
If the direction of flow of charge is inclined at an angle with the perpendicular, then
current density, $J=\frac{i}{\Delta S \cos\theta}$ or $I=\vec{J} \cdot \overrightarrow{\Delta S}$
Current density $J =\frac{ i }{\Delta S }$, where, $\Delta S$ is area of cross-section.
If the direction of flow of charge is inclined at an angle with the perpendicular, then
current density, $J=\frac{i}{\Delta S \cos\theta}$ or $I=\vec{J} \cdot \overrightarrow{\Delta S}$
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
The figure shows a plot of three curves a, b, c showing the variation of photocurrent vs collector plate potential for three different intensities I1, I2 and I3 having frequencies $\sqrt{1} ,\sqrt{2}$ and $\sqrt{3}$, respectively incident on a photosensitive surface.
→Point out the two curves for which the incident radiations have same frequency but different intensities.
Write the law of reflection.
Mark the correct options.
- The luminous efficiency of a monochromatic source is always greater than that of a white light source of same power.
- The luminous efficiency of a monochromatic source of wavelength 555nm is always greater than that of a white light source of same power.
- The illuminating power of a monochromatic source of wavelength 555nm is always greater than that of a white light source of same power.
- The illuminating power of a monochromatic source is always greater than that of a white light source of same power.
Write the formula to determine the value of electric field intensity due to a uniformly charged thin spherical shell.
Show variation of resistivity of Si with temperature in a graph.
What will be the relationship between the mass loss $\Delta M$ of a nucleus and its binding energy ( E )?
→Does the value of electric flux depend on the shape of the Gaussian surface?
Give two factors by which the voltage sensitivity of a moving coil galvanometer can be increased.
A photosensitive surface emits photoelectrons when red light falls on it. Will the surface emit photoelectrons when blue light is incident on it? Give reason.
An experimenter measures the length of a rod. In the cases listed, all motions are with respect to the lab and parallel to the length of the rod. In which of the cases the measured length will be minimum?
- The rod and the experimenter move with the same speed v in the same direction.
- The rod and the experimenter move with the same speed v in opposite directions.
- The rod moves at speed v but the experimenter stays at rest.
- The rod stays at rest but the experimenter moves with the speed v.