Continuous (direct) current

Electromotive force
Ε = A / q
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Electromotive force - potential difference
Ε = φ1 - φ2
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Current intensity (strength)
I = Δ_q / Δ_t
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Current intensity (strength)
I = e n v S
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Electric current density
j = I / S
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Electric current density
j = e n v
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Resistance
R = ρ l / S
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Electrical conduction
λ = 1 / R
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Resistance and temperature
R = R0(1 + α t)
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Specific resistance
ρ = ρ0(1 + α t)
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Specific conduction
σ = 1 / ρ
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Connection in series: current intensity
I1 = I2
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Connection in series: voltage
U = U1 + U2
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Connection in series: resistance
R = R1 + R2
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Parallel connection: current intensity
I = I1 + I2
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Parallel connection: voltage
U1 = U2
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Parallel connection: current intensity and resistance
I1 / I2 = R2 / R1
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Parallel connection: current resistance
1/R = 1/R1 + 1/R2
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Parallel connection: current resistance
R = R1 * R2 / (R1+R2)
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Ohm's law
I = U / R
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Ohm's law for closed circuit
Ε = I*R + Ir
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Ohm's law for closed circuit: many current sources
nΕ = I*R + Inr
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Work of electric current
A = Δ_q * U
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Work of electric current
A = I*R^2 *t
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Work of electric current
A = U^2 * t / R
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Power of electric current
P = U * I
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Power of electric current
P = I^2 * R
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Power of electric current
P = U^2 / R
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Work and power of electric current
A = P t
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