Question
What is electric current ? Explain about it.
✓
Answer
→To understand electric current, imagine a small area held normal (Perpendicular) to the direction of flow of charges.
→Both the positive and the negative charges may flow forward and backward across the area.
→Let $q_{+}$be the net amount of positive charge that flows in the forward direction across the area Similarly, let $q_{-}$be the net amount of negative charge flowing across the area in the forward direction.
→The net amount of charge flowing across the area in the forward direction in the time interval t , is
$q=q_{+}-q_{-}$
→For steady current, electric charge is proportional to time. so,
$\begin{array}{l}
\therefore q \propto t \\
\therefore I =\frac{q}{t}
\end{array}$
→Electric current : "The amount of electric charge passing perpendicularly through the cross-section of a conductor per unit time is called electric current."
→An electric current which does not change with time is called steady current.
→Currents are not always steady. In that case, average value or instantaneous value of current has to be considered.
→Let $\Delta Q$ be the net charge flowing across $a ^{\prime}$ cross- section of a conductor during the time interval $\Delta t$, then the average current flowing through the conductor is
$< I >=\frac{\Delta Q }{\Delta t}$
→The current at time $t$ across the cross- section of the conductor is defined as the value of the ratio of $\Delta Q$ to $\Delta t$ in the limit of $\Delta t$ tending to zero. So, instantaneous current
$\begin{aligned}
I & =\lim _{\Delta t \rightarrow 0} \frac{\Delta Q }{\Delta t} \\
\therefore I & =\frac{d Q }{d t}
\end{aligned}$
→The unit of electric current is ampere (A) and current is a scalar quantity.
→An ampere is typically the order of magnitude of currents in domestic appliances.
→An average lighting carries currents of the order of tens of thousands of amperes $\left(\sim 10^4 A\right.$ ).
→Currents in nerves of our body are in the order of microamperes. $\left(\sim 10^{-6} A\right)$
→Both the positive and the negative charges may flow forward and backward across the area.
→Let $q_{+}$be the net amount of positive charge that flows in the forward direction across the area Similarly, let $q_{-}$be the net amount of negative charge flowing across the area in the forward direction.
→The net amount of charge flowing across the area in the forward direction in the time interval t , is
$q=q_{+}-q_{-}$
→For steady current, electric charge is proportional to time. so,
$\begin{array}{l}
\therefore q \propto t \\
\therefore I =\frac{q}{t}
\end{array}$
→Electric current : "The amount of electric charge passing perpendicularly through the cross-section of a conductor per unit time is called electric current."
→An electric current which does not change with time is called steady current.
→Currents are not always steady. In that case, average value or instantaneous value of current has to be considered.
→Let $\Delta Q$ be the net charge flowing across $a ^{\prime}$ cross- section of a conductor during the time interval $\Delta t$, then the average current flowing through the conductor is
$< I >=\frac{\Delta Q }{\Delta t}$
→The current at time $t$ across the cross- section of the conductor is defined as the value of the ratio of $\Delta Q$ to $\Delta t$ in the limit of $\Delta t$ tending to zero. So, instantaneous current
$\begin{aligned}
I & =\lim _{\Delta t \rightarrow 0} \frac{\Delta Q }{\Delta t} \\
\therefore I & =\frac{d Q }{d t}
\end{aligned}$
→The unit of electric current is ampere (A) and current is a scalar quantity.
→An ampere is typically the order of magnitude of currents in domestic appliances.
→An average lighting carries currents of the order of tens of thousands of amperes $\left(\sim 10^4 A\right.$ ).
→Currents in nerves of our body are in the order of microamperes. $\left(\sim 10^{-6} A\right)$
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 person wears glasses of power -2.5D. Is the person farsighted or nearsighted? What is the far point of the person without the glasses?
Explain how does the polarized dielectric modify the original external field inside it ?
The dielectric strength of air is 3.0 × 106V/m. A parallel-plate air-capacitor has area 20cm2 and plate separation 0.10mm. Find the maximum rms voltage of an AC source that can be safely connected to this capacitor.
Two small identical electrical dipoles AB and CD, each of dipole moment 'p' are kept at an angle of 120o as shown in the figure. What is the resultant dipole moment of this combination? If this system is subjected to electric field ($\overrightarrow{\text{E}}$) directed along +X direction, what will be the magnitude and direction of the torque acting on this?
→
Obtain expression of self inductance of a solenoid having length $l$ and cross-section of area A .
→State the principle of working of a cyclotron. Write two uses of this machine.
The weather report reads, "Temperature 20°C : Relative humidity 100%". What is the dew point?
If the intensity of light falling on a metal plate is doubled, what will be the effect on photocurrent and maximum kinetic energy of emitted photoelectrons?
A simple microscope using a single lens often shows coloured image of a white source. Why?
Determine the distance of closest approach when an alpha particle of kinetic energy 4·5 MeV strikes a nucleus of Z = 80, stops and reverses its direction.