Example 1
ΔΦ = 0.02 Wb, Δt = 0.01 s -> |ε| = 2 V.
Electromagnetic induction calculator
Type the flux change |ΔΦ| [Wb] and the time Δt [s]. The calculator computes Faraday’s law |ε| = |ΔΦ|/Δt: 0.02 Wb in 0.01 s is 2 V, and in 0.1 s it is 0.2 V. Zero seconds does not divide.
Transformer: U2 = U1 n2/n1. Reactance: XL = 2πfL.
Result
Flux change |ΔΦ| (Wb) and Time Δt (s). The result shows up here.
How it works
Faraday in this calculator is the magnitude: |ε| = |ΔΦ|/Δt. At 0.02 Wb in 0.01 s you get 2 V. At 0.02 Wb in 0.1 s you get 0.2 V: ten times longer, ten times smaller EMF. At 1 Wb in 0.5 s you get 2 V again. 1 V = 1 Wb/s.
Two fields: |ΔΦ| in webers, Δt in seconds. The result is in volts. A comma and a period in 0.02 are the same flux. The sign of EMF (Lenz, the minus in ε = −dΦ/dt) does not enter the result: the calculator reports the magnitude.
Δt must be positive. Zero does not divide. Both fields need a number before 2 V can appear. A faster flux change at the same |ΔΦ| gives a larger EMF.
Transformer U2 = U1 n2/n1 is on the neighbouring page and computes a turns ratio, not ΔΦ/Δt. XL = 2πfL is coil reactance at frequency f, not Faraday induction. Lorentz force F = B I l is force on a wire, not a volt.
At 0.2 Wb in 0.02 s, |ε| = 10 V. At 0.005 Wb in 0.02 s it is 0.25 V. At 0.001 Wb in 0.001 s it is 1 V. At 0.08 Wb in 0.04 s it is 2 V again.
Type 0.02 and 0.01, click Calculate, and match 2 V. Then stretch Δt to 0.1 s and see 0.2 V. The current I = Q/t that this EMF can drive is a separate step.
How to use
- In the first field enter the flux change |ΔΦ| in webers, for example 0.02.
- In the second field enter the time Δt in seconds, for example 0.01.
- Click Calculate. The calculator computes |ΔΦ|/Δt. 0.02 Wb and 0.01 s give 2 V.
- Δt must be positive. Zero does not divide. Both fields need a number.
- Want U2 from turns? Open the transformer page. Here it stays EMF from flux change.
Formula
|ε| = |ΔΦ| / Δt
ε = −dΦ/dt (Lenz). Δt > 0, |ΔΦ| > 0. 1 V = 1 Wb/s.
ε, ΔΦ, and Δt in Faraday’s law
Electromagnetic induction here is |ε| = |ΔΦ|/Δt. 0.02 Wb in 0.01 s is 2 V. In 0.1 s it is 0.2 V. 1 V = 1 Wb/s.
- ε
- EMF [V], magnitude here. 0.02 / 0.01 = 2 V. The Lenz sign does not enter the calculator.
- ΔΦ
- Flux change [Wb]. 0.02 Wb. Faster change, larger |ε|.
- Δt
- Change time [s]. 0.01 s or 0.1 s. Δt must be positive.
Real-life examples
Example 2
ΔΦ = 0.02 Wb, Δt = 0.1 s -> |ε| = 0.2 V.
Example 3
ΔΦ = 1 Wb, Δt = 0.5 s -> |ε| = 2 V.
Example 4
ΔΦ = 0.005 Wb, Δt = 0.02 s -> |ε| = 0.25 V.
Example 5
ΔΦ = 0.2 Wb, Δt = 0.02 s -> |ε| = 10 V.
Example 6
ΔΦ = 0.001 Wb, Δt = 0.001 s -> |ε| = 1 V.
Example 7
ΔΦ = 0.08 Wb, Δt = 0.04 s -> |ε| = 2 V.
Example 8
ΔΦ = 0.5 Wb, Δt = 0.05 s → |ε| = 10 V.
Ways to use this calculator
- You compute 2 V from 0.02 Wb in 0.01 s.
- You compare with a slower change: 0.02 Wb in 0.1 s is 0.2 V.
Frequently asked questions
How much |ε| at 0.02 Wb and 0.01 s?
EMF is 2 V. That is 0.02 / 0.01. At 0.02 Wb and 0.1 s you get 0.2 V: ten times the Δt, one tenth the |ε|.
Which units do I type?
Flux change |ΔΦ| [Wb], time Δt [s]. Result |ε| [V]. One volt is 1 Wb/s. Type a millisecond as 0.001, not as 1.
What if Δt = 0?
The calculator refuses zero seconds. |ε| = |ΔΦ|/Δt at zero time does not exist. Both fields need a number.
Does the calculator give the sign of EMF?
No. It computes the magnitude. The Lenz sign, ε = minus dΦ/dt, sits in the formula, not in the result.
How is this different from U2 = U1 n2/n1?
Here EMF from flux change over time. There the turns ratio of an ideal transformer, with no ΔΦ field.
How is this different from XL = 2πfL?
Here induction from ΔΦ and Δt. There coil reactance at a known f. Different fields, even though both cards talk about induction.
How much at 1 Wb and 0.5 s?
EMF is 2 V. At 0.2 Wb and 0.02 s you get 10 V. A large flux in a short time drives |ε| up.
Does a comma in 0.02 work?
Yes. 0.02 and 0,02 are the same |ΔΦ| [Wb]. A comma and a period mean the same value.
How much at 0.005 Wb and 0.02 s?
EMF is 0.25 V. At 0.001 Wb and 0.001 s you get 1 V. A small flux, a short Δt.
Where is Lorentz force?
On F = B I l. Here EMF in volts from dΦ/dt, not a force on a wire in teslas.
Knowledge sources
The formula is the school one. Units follow SI; NIST SP 330 and BIPM define the measures, not your result.
Page updated in 2026.