Continuous (direct) current

$$I = e\cdot n\cdot v\cdot S$$

Current intensity (strength)

I - current intensity
e - electron charge
n - concentration of charged particles
v - speed (velocity)
S - cross-sectional area

Find It is known that:

$$R = \frac{\rho\cdot l}{S}$$

Electric current density

$$j = \frac{I}{S}$$

j - current density
I - current intensity
S - cross-sectional area

Find It is known that:

Calculate 'j'

Electric current density

$$j = e\cdot n\cdot v$$

j - current density
e - electron charge
n - concentration of charged particles
v - speed (velocity)

Find It is known that:

Calculate 'j'

Resistance

R - resistance
ρ - specific resistance
l - length
S - cross-sectional area

Find It is known that:

$$\lambda = \frac{1}{R}$$

Electrical conduction

λ - electrical conduction
R - resistance

Find It is known that:

Calculate 'λ'

Resistance and temperature

$$R = R0\cdot (1+\alpha\cdot t)$$

R - resistance
R0 - resistance when temperature is 0 C
α - temperature coefficient of resistance
t - temperature

Find It is known that:

$$\rho = \rho0\cdot (1+\alpha\cdot t)$$

Specific resistance

ρ - specific resistance
ρ0 - specific resistance when temperature is 0 C
α - temperature coefficient of resistance
t - temperature

Find It is known that:

Calculate 'ρ'

Specific conduction

$$\sigma = \frac{1}{\rho}$$

σ - specific conduction
ρ - specific resistance

Find It is known that:

Calculate 'σ'

Connection in series: current intensity

$$I1 = I2$$

I - current intensity

Find It is known that:

Calculate 'I1'

Connection in series: voltage

$$U = U1+U2$$

U - voltage
U1, U2 - voltage for series elements

Find It is known that:

Calculate 'U'

Connection in series: resistance

$$R = R1+R2$$

R - resistance
R1, R2 - resistance for series elements

Find It is known that:

Parallel connection: current intensity

$$I = I1+I2$$

I - current intensity
I1, I2 - current intensity for individual elements

Find It is known that:

Parallel connection: current intensity and resistance

Parallel connection: voltage

$$U1 = U2$$

U - voltage

Find It is known that:

Calculate 'U1'

$$\frac{I1}{I2} = \frac{R2}{R1}$$

I1, I2 - current intensity for individual elements
R1, R2 - resistance for individual elements

Find It is known that:

Calculate 'I1'

Parallel connection: current resistance

$$\frac{1}{R} = \frac{1}{R1}+\frac{1}{R2}$$

R - resistance
R1, R2 - resistance for individual elements

Find It is known that:

Parallel connection: current resistance

$$R = \frac{R1\cdot R2}{R1+R2}$$

R - resistance
R1, R2 - resistance for individual elements

Find It is known that:

Ohm's law

$$I = \frac{U}{R}$$

I - current intensity
U - voltage
R - resistance

Find It is known that:

$$E = I\cdot R+I\cdot r$$

Ohm's law for closed circuit

Ε - electromotive force
I - current intensity
R - external resistance
r - inner (internal) resistance of current source

Find It is known that:

Calculate 'Ε'

Ohm's law for closed circuit: many current sources

$$n\cdot E = I\cdot R+I\cdot n\cdot r$$

n - number of current sources
Ε - electromotive force
I - current intensity
R - external resistance
r - inner (internal) resistance of current source

Find It is known that:

Calculate 'n'

Work of electric current

$$A = \Delta_{q}\cdot U$$

A - work
q - charge
U - voltage

Find It is known that:

$$A = I\cdot R^{2}\cdot t$$

Work of electric current

A - work
I - current intensity
R - resistance
t - time

Find It is known that:

$$A = \frac{U^{2}\cdot t}{R}$$

Work of electric current

A - work
U - voltage
t - time
R - resistance

Find It is known that:

Power of electric current

$$P = U\cdot I$$

P - current power
U - voltage
I - current intensity

Find It is known that:

Calculate 'P'

Power of electric current

$$P = I^{2}\cdot R$$

P - current power
I - current intensity
R - resistance

Find It is known that:

Calculate 'P'

Power of electric current

$$P = \frac{U^{2}}{R}$$

P - current power
U - voltage
R - resistance

Find It is known that:

Calculate 'P'

Work and power of electric current

$$A = P\cdot t$$

A - work
P - current power
t - time

Find It is known that: