coil voltage calculator
Calculate coil voltage for DC and AC coils from resistance, current, inductance, and frequency. Handles V=IR, impedance, and induced/back-EMF estimates.

coil impedance calculator
Voltage of a coil can be found using simple formulas: V = I*R in DC and V rms = I rms * Sqrt[ (R ) 2 + (w L ) 2 ] in AC and V L = L( dI/ dt ) to approximate transient/back-EMF spikes.
Formula & Table Summary:
- DC: V = I × R
- AC: ω = 2πf, Z = √(R² + (ωL)²), V_rms = I_rms × Z
- Transient: V_L = L · dI/dt
- Power loss: P = I_rms² × R
Units: V (volts), I (A), R (Ω), L (H), f (Hz). Add protection (diode/snubber) for inductive loads.
coil current to voltag
A Coil Voltage Calculator calculates the voltage across coils in terms of DC (V = IxxR), AC using impedance V rms = I rms x and transient/back-EMF (V L = L dI d t ). Use it to estimate heating (P = I 2 R), size drivers and predict spikes.
coil resistance voltage
R (Ω) | I (A) | L (mH) | f (Hz) | Calculation | Voltage (V) |
---|---|---|---|---|---|
2.0 | 1.5 | — | — | V = 1.5 × 2.0 | 3.00 |
5.0 | 0.5 | 10 | 1000 | ω=6283; Z≈5.00; V=0.5×5.00 | 2.50 |
1.2 | — | 10 | — | V_L = 0.01 × 1000 (dI/dt) | 10.0 |
Frequently Asked Questions - coil voltage calculator:
How do I calculate coil voltage for DC?
Use V = I × R, where I is steady current and R is coil resistance.
How to calculate coil voltage for AC?
Compute Z = √(R²+(ωL)²) with ω=2πf, then V_rms = I_rms × Z.
What is back-EMF in coils?
Back-EMF is the induced voltage V_L = L·dI/dt generated when current changes in the coil.
How to estimate transient spikes?
Use V_L = L·dI/dt with worst-case dI/dt; include supply and clamp voltages for total stress.
What units should I use?
Use volts (V), amperes (A), ohms (Ω), henries (H), hertz (Hz), and A/s for dI/dt.
How to size a driver voltage?
Use V_rms from impedance at operating frequency and allow margin for back-EMF and driver headroom.
Does inductance always increase voltage?
At AC or during transients, inductance increases impedance or causes induced voltage; steady DC sees only resistance.
How do I reduce back-EMF spikes?
Add flyback diodes (DC), snubbers, RC networks, TVS diodes or active clamp circuits.
How to calculate coil power loss?
Use P = I_rms² × R to estimate resistive (I²R) heating losses.
Can I measure coil resistance easily?
Yes — disconnect the coil and measure DC resistance with an ohmmeter; use low-current meters for low-resistance coils.
Related Posts

Horsepower Calculator
Convert between horsepower, kW, watts, torque, and RPM. Supports mechanical/electrical HP, single- and three-phase, plus quick HP↔kW conversions.

over load current calculator
Calculate overload current using I OL =I FL*SF, where I FL is full-load current and SF is the service factor or overload multiplier.

CT Ratio Calculator
Calculate the CT secondary current from the primary current and the CT ratio, or find the correct CT ratio for your system. Includes formulas, tables, and examples.

current imbalance calculator
Calculate percentage current imbalance in three-phase systems using % I imb= {(Imax - Iavg) / Iavg} * 100

current calculator
Easily calculate electrical current using Ohm’s Law:𝐼= 𝑉/R, with instant results for amps from voltage, resistance, or power.

step down voltage calculator
Easily calculate output voltage when stepping down AC or DC using transformers or voltage dividers. Ideal for electronics, power supply design, and safety.