Unit 2: Inductance and Inductive Reactance

TRUE/FALSE

	1.	When the varying lines of magnetic force from a coil induce an EMF in an adjacent coil, the coils have mutual inductance.

ANS:	T	PTS:	1	REF:	Lenz's Law

	2.	In a step-up transformer, the primary voltage is greater than the secondary voltage.

ANS:	F	PTS:	1	REF:	Lenz's Law

	3.	A circuit or coil has an inductance of one henry when current varying at the rate of one ampere per second induces an EMF of 120 volts across the terminals of the circuit or coil.

ANS:	F	PTS:	1	REF:	Measurement of Inductance

	4.	The vectors shown in the accompanying figure represent 110 volts with a current of 10 amperes leading by 90°.

ANS:	F	PTS:	1	REF:	Vector Representation

COMPLETION

	1.	The amount of opposition to current change is called ____________________ and is a function of frequency and inductance.

ANS:	 inductive reactance

PTS:	1	REF:	Objectives

	2.	According to Lenz’s law, the ____________________ in a coil always flows in the opposite direction of the effect that produces it.

ANS:	induced voltage

PTS:	1	REF:	Lenz's Law

	3.	The unit of inductance is the ____________________.

ANS:	
henry (H)
H
henry

PTS:	1	REF:	Lenz's Law

	4.	The opposition in coils having inductance can be measured in ____________________.

ANS:	ohms

PTS:	1	REF:	Lenz's Law

SHORT ANSWER

	1.	How can you change the inductance of a coil?

ANS:	
The inductance can be varied by varying the amount of magnetic flux or the number of turns in the coil.

PTS:	1	REF:	Lenz's Law

	2.	What is the difference between self-inductance and mutual inductance?

ANS:	
In a current-carrying coil, when the varying lines of magnetic force induce an EMF in the coil itself, the coil has self-inductance. Mutual inductance occurs when the varying lines of magnetic force from a coil induce an EMF in an adjacent coil.

PTS:	1	REF:	Lenz's Law