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^Electrolysis

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Electrolysis

  • The process of dissociating a liquid into ions when electric current is passed through them is called electrolysis or conductors of second kind. The arrangement used to study electrolysis is called a Voltameter. It contains a vessel, two electrodes, a solution called electrolyte & dc power supply.
  • Current inside electrolytes is due to motion of both + ve & – ve ions. i.e. I = I+ + I–  also I+ ≠ I–. 
  • Electrolysis obey Ohm’s law for small currents if V applied > V back.
  • Conductivity of electrolytes is 105  to 106 times smaller than that of metallic conductors.

^Ammeter

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Ammeter

(a) Constructed by connecting small resistance called shunt (S) in parallel to a galvanometer.

(b) Ig G = (I – Ig) S

(c)

(d) Used in series with the resistor whose current is to be measured.

^CR circuits

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With switch S thrown towards A, capacitor undergoes charging in accordance with

With switch S thrown towards B, capacitor undergoes discharging in accordance with

Here CR = t is called capacitive time constant.

Following table is useful to solve problems based on exponential functions.

^n – cells in series

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n – cells in series

As all the cell supply current in same direction thus

^Significant figures

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^Significant figures

All accurately known digits plus the first uncertain digit of a measurement is called significant digits or significant figures. e.g. if in a measurement, mass of a body lies between 5.6 kg & 5.7 kg & we estimate it as 5.62 kg then the first two digits 5 & 6 are certain while the third digit 2 is approximately known we can say there are 3 significant figures.

Following are the rules for counting significant figures

Rule 1: All non zero digits are significant.

Rule 2: All zeros occuring between two non zero digits are significant.

Rule 3: The digit zero (underlined) conventionally put on the left of a decimal for a number less than one is never significant. All zeros to the right the decimal point are not significant.

Rule 4: The terminal or trailing zero(s) in a number without a decimal point are not significant.

Rule 5: The trailing zero(s) in a number with a decimal point are significant.

Rule 6: The powers of ten are not significant.

Rule 7: No. of significant figures remains unchanged on changing the units of measurement, zeroes appearing in the base number in the scientific notation are significant.

Example NSD Using rule
4567 Four 1
450067 Six 2
0.004567 Four 3
456700 Four 4
0.00456700 Six 5
4.5 x 10 – 6 Two 6
5.300 x 10 6 mm Four 7

^Ohm’s law

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Ohm’s law

(a) = constant called electrical resistance R, provided there is no change in the physical conditions like temperature, pressure & impurity etc.

(b) = (Microscopic version) i.e. conductivity of a conductor is independent of electric field existing in the material over a wide range of field.

^Energy (potential) stored in a capacitor

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Energy (potential) stored in a capacitor

A charged capacitor of any shape or size stores energy (potential) in the form of electrostatic electric field, it is given by

Energy per unit volume is called energy density, it is Electric energy density,

^PPC with a metal slab in plates

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PPC with a metal slab in plates

If a metal slab (dielectric constant K = ∞), thickness t < d is placed between the plates of a PPC, then due to the electric field between the capacitor plates the dielectric gets polarized & an electric equal to E0 is induced in it, as a consequence net electric field in dielectric is found to be zero i.e. Enet = 0.

Due to this field electric field net potential difference across the capacitor plates becomes

Using C = q/V, capacitance of capacitor becomes

If the conducting slab occupies the entire space available between the plates of capacitor i.e. when t =d & K = ∞, then C = ∞

Comparing (a), (b) & (c) we can say

CDS > CCS > Co

^What is a vector?

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^What is a vector?

If both magnitude and direction are required to completely described a physical quantity, then it is called a vector. A vector quantity is represented by putting on arrow above it or by bold letter e.g. it Q is vector then we represent it as  or Q. if a quantity can have any direction it is called polar. If its direction is along axis only then called axial.

^Dimensionless Quantities

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^Dimensionless Quantities

Strain, angle, solid angle, all Trigonometric ratios, all real numbers, logarithmic functions, exponential functions, Poisson’s ratio, refractive index, relative density, relative permittivity, relative permeability, fine structure constant etc. have no dimensions.

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