Topic 1 Transformers

Explain the transformer rule.

Topic 2 Reactance

Define the reactance of a

(a) coil

(b) capacitor

Topic 3 Impedance

(a) Show how to add inductive reactance and capacitive reactance to resistance.

(b) Show how to calculate the phase angle between voltage and current in a reactive circuit.

Examples

A household doorbell transformer produces 15 VAC to operate a doorbell that uses 1.5 A when your visitor presses the button beside your front door. That is much safer than the 120 VAC If the secondary of the transformer has 100 turns, how many turns

A fluorescent lamp ballast is an inductance coil that limits the current through a 40 W lamp to the appropriate value for 120 VAC at  60 Hz. What is the inductive reactance and inductance of the coil?

A capacitor is used in a hi-fi speaker crossover to send high frequency audio signals to a tweeter speaker. If the capacitive reactance is to be 8 Ω at 1.0 kHz, what is the capacitance?

A capacitor and a resistor are connected in series in the feedback circuit of an operational amplifier. If the resistance and capacitive reactance are both 10 kΩ at 20 kHz, what is the capacitance of the capacitor and the impedance of the series circuit at that frequency?

Textbook Problems