🔍 Key Concepts

• Bourdon tube construction and shape (curved, flattened tube sealed at one end) • How internal pressure affects the curvature of a thin, curved metal tube • Which motion at the free end of the tube will move the linkage and pointer shown in GS-0114

💭 Think About

• Look at the illustration and imagine pressure entering at the connection fitting: in which direction must the free end of the tube move to rotate the gear and pointer? • Think about what a curved, springy metal tube wants to do when it is pressurized from the inside: does it tend to become straighter or more tightly curved? • Compare each answer choice with the motion needed to increase the indicated pressure on the dial—would the tube need to curl more or straighten out to show higher pressure?

✅ Before You Answer

• Verify where the fixed end and free end of the Bourdon tube are located in the illustration (at the socket vs. at the linkage). • Confirm whether the tube’s motion is primarily curving/uncurving or sliding linearly—this will eliminate choices that mention only linear expansion or contraction. • Check that the selected choice matches the motion that would rotate the segment gear and pointer in the direction of increasing pressure on the dial.