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Question

Difficulty: HardSwitches and Relays

In an electromechanical relay, energizing the coil produces a magnetic field that pulls the armature, which causes the normally closed (NC) contacts to establish circuit continuity and the normally open (NO) contacts to break circuit continuity.

Answer: Answer

Answer

False
The statement is false because the descriptor 'normally' refers to the unenergized resting state of the relay. When current energizes the electromagnetic coil, the armature moves to close normally open (NO) contacts—completing that circuit—and open normally closed (NC) contacts—interrupting that circuit.

Step-by-Step Solution

1
Identify the baseline resting (de-energized) state of relay contacts
Normally open (NO) contacts are open (no continuity) and normally closed (NC) contacts are closed (continuity present) when the coil carries no current.
The term 'normally' specifies the default mechanical condition of the contacts prior to coil energization.
2
Analyze the mechanical effect of coil energization
Current flowing through the coil generates an electromagnetic field that pulls the movable armature toward the core.
Electromagnetic attraction provides the physical force required to switch contact positions.
3
Determine the resulting contact states when energized
Armature displacement forces NO contacts to close (establishing continuity) and NC contacts to open (breaking continuity).
Energization transitions all contact pairs to the state opposite their resting configuration.
4
Compare the derived operation with the given statement
The statement asserts that energization causes NC contacts to establish continuity and NO contacts to break continuity, which is the exact inverse of actual relay operation.
Because the statement inverts the functional behavior of NO and NC contacts during coil activation, it is false.

Key Concept

Electromechanical Relay Contact States (NO vs. NC) During Coil Energization
Estimated Time:1m 15s
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Topics

Switches and Relays

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