EE115W4A Inductance of a Coil Sample Assignment

1. Calculate the inductance of a coil that induces 120V when the current through it changes at a rate of 5A/s.

L = VL/(di /dt)

120V/5A/s = 24 H

2. Calculate the inductance of a coil that induces 850V when the current through itchanges at a rate of 30mA in 2µs.

L = VL/(di/dt)

850V/ (30mA/2µs )= 0.05667H = 56.66 mH

3. Given an iron core with 200 turns, a length of 0.35m and an area of 3x10-4m2,determine the inductance.

N = 200 turns

l = 0.35m

A = 3*10-4m2

L = (N2* A/l) * 1.26µ1* (2002* 3*10-4/ 0.35) * 1.26µ = 4.32 µH

4. A 10:1 transformer has NP= 300, VP= 240V and IP= 2A. Determine NS, VS, and Is.

Ns= 300 / 10 = 30 turns

Vs= 240V / 10 = 24 V

Is= Vs/R1= 24V / 10/Ip= 24V / 5 = 4.8A

5. Four inductors of values 6mH, 7mH, 9mH, and 10mH are connected in series. Determine the total inductance.

L_{T =} L₁+  L₂ + L₃ + L_4….etc.

L_T = 6mH + 7mH + 9mH + 10mH = 32mH or 0.032H

6. Four inductors of values 6mH, 7mH, 9mH, and 10mH are connected in parallel. Determine the total equivalent inductance.

1/L_T = 1/L₁ + 1/L₂ + 1/L₃ + 1/L_4…..etc.

L_T =1 / 1/L₁ + 1/L₂ + 1/L₃ + 1/L₄

L_T = 1 / 1/ 6mH + 1/7mH + 1/9mH + 10mH

L_T = 1.92073170mH or 1920.73170µH

7. Calculate the energy store in a 20mH inductor with a current of 3mA flowing through it.

W = ½ L I²

Where :

W = energy stored ( joules, J)

L = inductance (henrys, H)

I = current ( amps, A)

W = ½ ( 20mH) (3mA)²

W = 90 J