Chemistry Figures Length Reading
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Ruler, caliper and micrometer figures for measuring length

Length Reading draws the instrument a length is read from: a centimeter or inch ruler with an object lying along it (marbles, a rock, a cube or a metal cylinder), a 150 mm caliper with its jaws open to the reading you type, or a 0–25 mm micrometer. On the ruler, students measure the object lined up with 0 or starting partway along, so they read both ends and subtract.

Metric ruler lengths can go one estimated digit past the smallest mark, for significant figures practice. The caliper reads to 0.1, 0.05 or 0.02 mm, with exactly one mark on its sliding scale lined up with the main scale, and the micrometer reads to 0.01 mm at its marks, or to an estimated 0.001 mm between them. Give a caliper or micrometer a zero error for a correction question. Close-ups of the scales keep the marks readable in print, and the answer key prints the reading.

What you can set

  • The instrument: a ruler, a caliper or a micrometer
  • A metric ruler, 15, 20, 30, 50 or 100 cm long, marked every 1 mm, 0.5 cm or 1 cm (or 5 or 10 cm on the long ones), read to one estimated digit or to the nearest mark
  • An inch ruler, 6, 8, 12 or 20 in long, marked every 1, 1/2, 1/4, 1/8 or 1/16 in
  • The object on the ruler, its length and left end, typed, picked at random, or set by dragging it along the ruler, with dashed lines down from its ends if you like
  • The caliper’s least count: 0.1 mm (10 divisions over 9 mm), 0.05 mm (20 over 39 mm) or 0.02 mm (50 over 49 mm), printed on the slider or left off
  • The micrometer read to its marks, 0.01 mm, or to one estimated digit past them, 0.001 mm
  • The caliper or micrometer reading, typed or picked at random, and a zero error, with the instrument also drawn closed
  • In the jaws: nothing, a block, a cylinder, a ball or a wire, drawn to size, with a short label
  • Magnifiers or close-ups of the scales, a chart title, and an answer key line

Copying, printing and sharing

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Example figures

Frequently asked questions

How do you measure with a ruler to the right number of significant figures?

Read to the smallest mark, then estimate one more digit. On a ruler marked in millimeters, that means reading to 0.01 cm, like 4.37 cm. On a ruler marked only every centimeter, read to 0.1 cm.

Can the object start somewhere other than 0?

Yes. Type where its left end sits, or drag the object along the ruler in the figure. Students then read both ends and subtract, and the answer key gives both ends as well as the length.

What are the dashed lines at the object’s ends for?

A marble or a rock touches the ruler below its widest point, so its ends sit above the marks they line up with. The dashed lines drop from each end down to the ruler to show where to read.

How do you read a caliper?

Read the main scale at the sliding scale’s zero: the last millimeter mark before it. Then find the one mark on the sliding scale that lines up exactly with a main-scale mark, and add that many least counts. With the zero just past 23 mm and the 9th mark of a 0.05 mm scale lined up, the reading is 23 + 9 × 0.05 = 23.45 mm.

How do you read a micrometer?

Read the last mark showing on the sleeve: whole millimeters above the datum line, and the half-millimeter mark below it if it has appeared. Then add the thimble mark on the datum line, 0.01 mm each. A sleeve showing 7 mm and thimble mark 38 read 7.38 mm; with the 7.5 mark showing as well, 7.88 mm. When the datum line falls between two thimble marks, estimate how far, in tenths of a mark, for one more digit: 0.4 of the way from mark 38 to mark 39 reads 7.384 mm.

What is a zero error?

With its jaws closed, a caliper or micrometer should read zero. If it doesn’t, the reading it shows closed is the zero error, positive or negative, and you subtract it from every reading: an instrument that reads +0.10 mm closed and 23.45 mm on a block measures 23.35 mm.

Can I make inch ruler questions with fractions?

Yes. Choose Imperial (in). Lengths land on a mark and are read as fractions of an inch, down to 1/16 in on the finest ruler.

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