Inductance (27-05-21) 1H

Inductance (27-05-21) 1H

Chapter Outline

1. Self-Inductance

2. RL Circuits

3. Oscillations in LC Circuit

1. Self-Inductance

When the current in a coil changes with time, an induced in the coil according to Faraday's law. The self-induced emf is:

 $e=-N\ \frac{\text{d}\Phi}{\text{d}t}=-L\ \frac{\text{d}I}{\text{d}t}$  

where L is the inductance of the coil. Inductance is a measure of how much oposition an electrical device offers to a change in current passing through the device.

Inductance has the SI unit of henry (H), where 1H = 1 V.s/A
The inductance of any coil is

 $L\ =\ \frac{N\Phi_B}{I}$  
where  $\Phi_B$  is the magnetic flux through the coil and N is the total number of turns. The inductance of a device depends on its geometry. For example, the inductance of an air-core solenoid is
 $L\ =\ \mu_0\ \frac{N^2A}{l}$  
where  $A$  is the cross-sectional area, and  $l$  is the length of the solenoid.

Multiple Select

Which of the following formula refer to self-induced emf?

• a. $L\ =\ \mu_0\ \frac{N^2A}{l}$

• b. $L\ =\ \frac{N\Phi_B}{I}$

• c. $e=-L\ \frac{\text{d}I}{\text{d}t}$

• d. $e=-N\ \frac{\text{d}\Phi}{\text{d}t}$

Multiple Choice

Which of the following formula refer to inductance of any coil?

• a. $L\ =\ \mu_0\ \frac{N^2A}{l}$

• b. $L\ =\ \frac{N\Phi_B}{I}$

• c. $e=-L\ \frac{\text{d}I}{\text{d}t}$

• d. $e=-N\ \frac{\text{d}\Phi}{\text{d}t}$

Multiple Choice

Which of the following formula refer to inductance of air-core solenoid?

• a. $L\ =\ \mu_0\ \frac{N^2A}{l}$

• b. $L\ =\ \frac{N\Phi_B}{I}$

• c. $e=-L\ \frac{\text{d}I}{\text{d}t}$

• d. $e=-N\ \frac{\text{d}\Phi}{\text{d}t}$

Let's try!

Answer in the next slide.

Multiple Choice

Answer to question 2 is

•  $1.36\ \mu H$  

•  $1.36\ H$  

•  $13.6\ \mu H$  

•  $136\ \mu H$  

Your Homework! (HW1)

https://forms.gle/s4mWBcLzTa5Am2cw7