Chapter 3: Current Electricity
NCERT Class 12 Physics, Part I, Chapter 3. 9 lessons, 19 narrated 3D videos, 14 simulations and 19 quiz questions, following the textbook section by section.
- Electric currentSo far our charges have sat still. Now let them move. A flash of lightning, the glow of a torch bulb, a signal running along a nerve: in each one, charges are flowing.
- Ohm’s lawIn 1828, Georg Simon Ohm studied how the current in a conductor depends on the voltage across it. Here is his experiment: a wire, a variable supply, an ammeter in series…
- Drift of electrons and resistivityZoom into a copper wire. Free electrons fly about between the fixed ions. At room temperature their random speeds are about 10⁵ metres per second.
- Resistivity of materials and temperatureOhm’s law, V equals I R, works beautifully for a metal wire. But it is not a law of nature like Newton’s laws. Many devices simply do not obey it.
- Electrical energy and powerSwitch on an electric heater and its coil glows red hot. The battery or the mains is handing energy to the coil. Let us find out how much, every second.
- Cells, emf and internal resistanceA steady current needs something to keep pushing charges round the circuit. That is the job of an electrolytic cell. Look inside one: two electrodes, P and N, dipped in…
- Kirchhoff’s rulesHere is a circuit with two cells and three resistors, joined in two loops. It is neither a simple series nor a simple parallel combination. How do we find the current in…
- The Wheatstone bridgeHere is a neat use of Kirchhoff’s rules. Four resistors are joined in a diamond. Call the corners A on the left, B at the top, C on the right and D at the bottom.
- The meter bridge and the potentiometerThis lesson is an extra topic. The meter bridge and the potentiometer are no longer in the current NCERT syllabus, but they are still used in school practicals and asked…