Even More Logical

Question 1

What are used in potential divider circuits to make the input into a logic gate high?

Answer 1

Switches, LDRs and thermistors

Question 2

What is the input to a logic gate when a switch is open or closed?

Answer 2

Open - low

Closed - input is connected directly to 5V supply

LDRs and thermistors work the same way

Question 3

How does a relay work?

Answer 3

• Current passes through a coil and the iron armature is attracted
• Armature pivots and pushes an insulating bar against the central contact
• The central contact moves, opening the normally closed contacts and closing the normally open contacts

Question 4

Why is a relay useful?

Answer 4

• Isolates logic circuit from high circuit to avoid damage
• Current output from logic gates is low but can be passed through a relay to switch on a larger current needed for motors, heaters, etc.