Ch 2Electrostatic Potential and Capacitance — Class 12 Physics, concept-first.

The previous sub-topic of this unit, Electric Charges and Fields, described the electrostatic field in terms of a VECTOR quantity, the electric field intensity , whose magnitude and direction had to b…

Electric potential at a point in an electrostatic field is defined as the work done by an EXTERNAL agent, per unit positive test charge, in bringing that test charge from infinity (where the field, an…

Because electric field and electric potential describe exactly the same electrostatic field, one as a vector and the other as a scalar, an exact mathematical relation must connect the two -- and it ta…

The potential due to a single, isolated point charge is the most fundamental potential formula in electrostatics, since the potential of any more complicated charge distribution is ultimately assemble…

An electric dipole consists of two equal and opposite point charges, and , separated by a small distance , characterised by its dipole moment , a vector of magnitude directed from the negative charge…

For any collection of point charges , located at distances from a point , the net electric potential at is found by the superposition principle, applied to a scalar quantity:

An equipotential surface is the set of all points in space that share exactly the same value of electric potential.

The electrostatic potential energy of a system of point charges is defined as the total work an external agent must do to assemble the charges, one at a time, bringing each one in from infinity to its…

When a dipole (dipole moment ) is placed in a UNIFORM external electric field , the two equal and opposite forces on its two charges are equal in magnitude and opposite in direction, so the NET force…

Every material is built from atoms and molecules, each with its own positively charged nucleus and surrounding negatively charged electrons -- but materials differ sharply in how easily those electron…

Although the charges inside a dielectric (insulator) are bound to their individual atoms or molecules and cannot travel through the material, an external electric field can still act on each of them l…

A capacitor is a device purpose-built to store electric charge (and, along with it, electrical energy), consisting of nothing more than two conductors -- called its plates or electrodes -- placed clos…

The parallel plate capacitor -- two identical, flat conducting plates, each of area , held parallel to each other a small distance apart -- is both the simplest capacitor geometry to analyse exactly a…

Beyond the flat-plate geometry, capacitors can equally well be built from spherical conductors, and the WBCHSE syllabus asks specifically for two related spherical cases: a single isolated conducting…

Exactly as resistors can be wired together in series or in parallel to obtain a resultant resistance different from any single available resistor, capacitors are routinely combined in a circuit to obt…

In a series combination, capacitors are connected end to end in a single chain, with only the two OUTER ends of the chain connected to the source of potential difference .

In a parallel combination, capacitors are connected between the very same pair of points -- all their "left" plates joined to one common node, and all their "right" plates joined to another common nod…

Charging a capacitor means gradually building up charge on its plates against the electrostatic field of the charge already present -- and, exactly as with any electrostatic process, the work done in…

Capacitors are not confined to physics problems -- devices built directly on the principle of storing charge (and energy) in a capacitor are used constantly in everyday life.

This chapter developed WBCHSE Unit 1's second sub-topic, moving from the scalar description of the electrostatic field through to the capacitor as a practical charge-storage device.

Sample papers and previous-year board questions for this subject.