E&M formulas

Question 1

charge =

Answer 1

amps * time

Question 2

Q=

Answer 2

it
Q = charge in coulombs C
i = current in amps (A)
t = time in seconds (s) “

Question 3

Time constant of resistor-capacitor combination

Answer 3

R*C

Question 4

Potential difference across a capacitor

Answer 4

Vs * e ^(t/time constant)

Question 5

Power =

Answer 5

IV

Question 6

V =

Answer 6

IR

Question 7

Time =

Answer 7

Energy / Power

Question 8

Electric field strength =

Answer 8

F/Q = V/Distance = q / 4pi8.85*10^-12 * r^2

Question 9

Electric potential =

Answer 9

q / 4pi8.85*10^-12 * r

Question 10

Electric potential energy =

Answer 10

q * q1 / 4pi8.85*10^-12 * r

Question 11

Charge being suspended between two parallel capacitor plates (electric field)

Answer 11

V = mgd/q = qE

Question 12

Charge being accelerated between two parallel capacitor plates

Answer 12

1/2mv^2 = Fd = qE = qV

Question 13

Force on a current carrying a conductor

Answer 13

BIL sin theta

Question 14

Formula for force on a charge in a magnetic field

Answer 14

BQV sin theta

Question 15

Magnitude of B field for a single conductor

Answer 15

Br = (4pi10^-7I) / 2pi*r

Question 16

Magnitude of B field for a coil

Answer 16

Br = (4pi10^-7NI) / 2*r

Question 17

Magnitude of B field for a solenoid

Answer 17

4pi10^-7(n/m)I

Question 18

Vrms =

Answer 18

Peak voltage / root(2)

Question 19

Irms =

Answer 19

Peak current / root (2)

Question 20

Peak voltage =

Answer 20

P2P voltage / 2

Question 21

Formula for transformers

Answer 21

“Vp / Vs = Np / Ns
where Vp = primary voltage, Vs is secondary voltage, Np is number of turns on the primary, Ns is the number of turns on the secondary”

Question 22

number of electrons =

Answer 22

Q / 1.602 * 10^-19

Question 23

Q =

Answer 23

Capacitance*V

Question 24

BQV

Answer 24

mv^2 / r