Potentiometer It is an arrangement used to measure accurate potential difference & is equivalent to an ideal voltmeter & based on null method. It is based on the principle that if a constant current is passed through a wire of uniform resistivity than potential difference across a given length of wire is directly proportional to […]
Sources of error The jockey should not be rubbed on the wire, as this resistance of wire will not remain uniform. Current should not be allowed to flow in the wire for a long time as this by producing heat will change the resistance of the wire. The value of resistor R is so selected […]
Wheatstone bridge It is the quadrilateral arrangement of four resistors P, Q, R & S connected to a cell & galvanometer G as shown. Here P & Q are called ratio arms, R known arm & S unknown arm. 1. If , then VC = VD & the bridge is said to be balanced i.e. […]
Voltmeter (a) Constructed by connecting a high value resistor (H) in series to a galvanometer. (b) V = I g ( G + H ) (c) RV = G + H → ∝ for ideal (d) Used in parallel across the resistor whose voltage is to be measured.
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.
Galvanometer A current carrying coil placed in a magnetic field experiences a torque & deflects. This deflection is calibrated to measure current flowing in it. Used to detect & measure only small currents of the order of microamperes. Current sensitivity (Is): It is defined as the deflection produced for a unit current. i.e. . Is […]
Fuse A fuse is a thin wire made up of an alloy of lead (75 %) & tin (25 %). Both its resistance and melting point are low. It is connected in series to the circuit in to protect the circuit from sudden strong currents by breaking the circuit. When the rate at which heat […]
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.
Finding net emf Here cells 1 & 2 are in parallel
^Instantaneous velocity Velocity a particular instant is called instantaneous. At any point instantaneous velocity acts along the tangent at that point. Mathematically it is measured as the limiting value of the average velocity. For motion along x – axis, Initial means, starting time i.e. t = 0 For 1 D motion along x – […]
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