The genius academy PHYSICS by Pradeep Kshetrapal
Formulas in current electricity (Direct Current)
1 Electric Current "q" is charge passing in normal direction
i=q/t
through a cross section of conductor in time "t"
2 Drift velocity Vd with Electric e is charge and m is mass on electron, E is
field Vd = electric field, τ is relaxation time.
3 Current I with Drift velocity Vd n is number density with of free electrons, A is
I = n e A Vd
area of cross section.
4 Mobility of charge “μ” μ = Vd / E =
5 Mobility and drift velocity Vd = μeE
6 Current and Mobility I= Ane x μeE
7 Resistance, P.D., and Current R=V/I V Potential Difference, I Current .
8 Resistance R with specific Res. l is length of conductor and A is area of cross
R=
section
9 Specific Resistance, ρ ρ=R
10 Resistivity with electrons ρ=
11 Current density J =I/ I is current, J current density, A is area of cross section
12 Current density magnitude J A cosθ = I θ is angle between and
13 Conductance G G = 1/R
14 Conductivity is specific resistance
15 Microscopic form of Ohms E is electric field
J= E
Law
16 Temperature coefficient of Ro is resistance at 0o C. Rt is resistance at to and
α=
Resistance “t” is temperature difference.
17 Resistances in series R = R1+R2+R3 Same current through all resistances (circuit Current
Resistances in parallel 1/Re = 1/R1 +1/R2 +1/R3 Same P.D. across each resistance (V of cell)
18 In a cell, emf and internal I is current, E is emf, R is external resistance, r
I=
resistance is internal resistance.
19 In a circuit with a cell V = E - Ir V is terminal potential difference
20 n Cells of emf E in series Emf = nE
21 Resistance of n cells in series r is internal resistance of one cell, R external
nr + R
Resistance
22 Current in circuit with n cells r is internal resistance of one cell, R external
I=
in series Resistance
23 n cells in parallel, then emf emf = E
24 n cells in parallel, resistance R + r/n R external resistance, r internal resistance
25 Cells in mixed group, condition n is number of cells in one row, m is number of
R=
for maximum current rows. r is internal resistance, R external resis.
26 Internal resistance of a cell r=( E is emf, V is terminal Potential difference, R is
external resistance.
27 Power of a circuit P = I.V = I2R = V2/R
28 Energy consumed E = I.V.∆T ∆T is time duration
29 Kirchoff Law (junction rule) Sum of currents at junction is zero.
30 Kirchoff Law (Loop rule) In a loop sum of all p.d.s is Zero
Formulas in current electricity (Direct Current)
1 Electric Current "q" is charge passing in normal direction
i=q/t
through a cross section of conductor in time "t"
2 Drift velocity Vd with Electric e is charge and m is mass on electron, E is
field Vd = electric field, τ is relaxation time.
3 Current I with Drift velocity Vd n is number density with of free electrons, A is
I = n e A Vd
area of cross section.
4 Mobility of charge “μ” μ = Vd / E =
5 Mobility and drift velocity Vd = μeE
6 Current and Mobility I= Ane x μeE
7 Resistance, P.D., and Current R=V/I V Potential Difference, I Current .
8 Resistance R with specific Res. l is length of conductor and A is area of cross
R=
section
9 Specific Resistance, ρ ρ=R
10 Resistivity with electrons ρ=
11 Current density J =I/ I is current, J current density, A is area of cross section
12 Current density magnitude J A cosθ = I θ is angle between and
13 Conductance G G = 1/R
14 Conductivity is specific resistance
15 Microscopic form of Ohms E is electric field
J= E
Law
16 Temperature coefficient of Ro is resistance at 0o C. Rt is resistance at to and
α=
Resistance “t” is temperature difference.
17 Resistances in series R = R1+R2+R3 Same current through all resistances (circuit Current
Resistances in parallel 1/Re = 1/R1 +1/R2 +1/R3 Same P.D. across each resistance (V of cell)
18 In a cell, emf and internal I is current, E is emf, R is external resistance, r
I=
resistance is internal resistance.
19 In a circuit with a cell V = E - Ir V is terminal potential difference
20 n Cells of emf E in series Emf = nE
21 Resistance of n cells in series r is internal resistance of one cell, R external
nr + R
Resistance
22 Current in circuit with n cells r is internal resistance of one cell, R external
I=
in series Resistance
23 n cells in parallel, then emf emf = E
24 n cells in parallel, resistance R + r/n R external resistance, r internal resistance
25 Cells in mixed group, condition n is number of cells in one row, m is number of
R=
for maximum current rows. r is internal resistance, R external resis.
26 Internal resistance of a cell r=( E is emf, V is terminal Potential difference, R is
external resistance.
27 Power of a circuit P = I.V = I2R = V2/R
28 Energy consumed E = I.V.∆T ∆T is time duration
29 Kirchoff Law (junction rule) Sum of currents at junction is zero.
30 Kirchoff Law (Loop rule) In a loop sum of all p.d.s is Zero
