^Electric cell
Electric cell It neither creates nor destroys charge, whereas it just maintains the potential difference & organized flow of charge by supplying energy.
Entries by kp-web-admin
^Parallel combination of resistors
Parallel combination of resistors The voltage is same across each circuit element is same but current is different & is inversely proportional to resistance of that part. V = V1 = V2 = V3 = I1R1 = I2R2 = I3R3 & Fact the maximum number of combination one can have, using all n – resistors […]
^Series combination of resistors
Series combination of resistors The current across each circuit element is same, but potential difference is different & proportional to resistance of that part. i.e. I = I1 = I2 = I3 & V1 = IR1, V2 = IR2, V3 = IR3 & R series = R1 + R2 + R3
^Zero α for Nichrome, constantan & Manganin
Zero α for Nichrome, constantan & Manganin i.e. there is appreciably no change (or very slight change) in R with temperature. 1. Constantan (or Eureka) ≡ Cu 60% & Ni 40% 2. Manganin ≡ Cu 84%, Mn 12% & Ni 4% 3. Nichrome ≡ Ni 67.5%, Cr 15%, Fe 16% & Mn 1.5%
^- ve α for electrolytes
– ve α for electrolytes Cause of decrease in R with increase in temp. for electrolytes is decrease in viscosity.
^- ve α for semiconductors
– ve α for semiconductors On heating semiconductors the number density of free electrons increases & τ decreases. But the effect of increase in ‘n’ is stronger than decrease in relaxation time (τ). Hence net effect is increase in ‘n’ which decreases resistance.
^Error in exponential form
^Error in exponential form Differentiating both sides we can write The maximum value of fractional error will be
^+ ve α for metals & alloys
+ ve α for metals & alloys With the increase in temperature of metals & alloys thermal agitation increases & hence the rate of collision increases. As a result the average time t between the successive collision decreases & hence the drift speed decreases, consequently the resistivity of metals increases.
^Temperature variation of resistance
Temperature variation of resistance On heating a material its resistivity changes, which changes the electrical resistance of the material. The electrical resistivity at temperature T can be calculated by using relation: ρT = ρ0 (1+ αT)
^Resistance of a wire on stretching
Resistance of a wire on stretching (a) increases n2 times original resistance if length is increased n times. (b) decreases n4 times if the radius of a wire is increased n times. Provided mass, density & resitivity wire are kept fixed.
About us
Our objective is to create a situation where students will find Physics interesting & the strongest subject helping them to achieve top ranks in competitive exams.
Courses We Offer
Contact Details
Copyright © 2021 KP Institute of Physics | Powered by RiAcub
