Image: Garry Gay/Getty Images
About This Quiz
Before GPS satellites and other high-tech navigational aids came on the market, people oriented themselves using compasses. A compass will point toward the North Pole and help you find your way. Which way will you be facing when you finish this quiz?
The magnet used in a magnetic compass is usually called:
the needle
A compass' small, lightweight magnet, or needle, is balanced on a nearly frictionless pivot point.
the pointer
the bar
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How do you know when the needle is pointing north?
The compass heats up.
The needle starts vibrating.
One end of the needle is colored to indicate it's pointing north.
One end of the needle is often marked "N," for north, or colored in some way to indicate that it points toward north.
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Why does a compass have a lightweight magnet and a frictionless bearing?
to make it easier to carry
to make the compass more affordable
to allow the needle to turn easier
The Earth's diameter is about 8,000 miles (12,875 kilometers), which is a long way for the planet's magnetic field to go before affecting your compass. That's why a compass has a lightweight magnet and a frictionless bearing -- otherwise, there just isn't enough strength in the Earth's magnetic field to turn the needle.
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According to a theory, what causes the Earth's magnetic forces?
the interaction of gravity with the sun and the moon
the rotational forces within the Earth's liquid iron layer
Convection caused by heat radiating from the Earth's core, along with the rotation of the Earth, may be what causes the liquid iron of the Earth's core to rotate and create a magnetic field.
the interaction of complicated wind patterns and ocean currents
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What's one way to change a needle (or other wirelike piece of steel) into a magnet?
rub it against another needle
stroke it with a magnet
You can magnetize a needle by stroking it with a magnet 10 to 20 times.
heat it and then quickly freeze it
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Ships and airplanes use what type of compass?
magnetic compass
gyroscopic compass
Because of the trouble encountered by magnetic compasses on moving platforms, many ships and planes instead use gyroscopic compasses.
pressurized compass
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What's one of the problems encountered by magnetic compasses on moving platforms?
the compasses correct themselves too slowly
Not only do magnetic compasses correct themselves slowly when the platform turns, but they also must be kept level to work properly.
the needles lose their magnetic force
the friction is too great
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What keeps a gyrocompass pointing in the same direction even when moved or rotated?
a gyroscope
A spinning gyroscope inside the compass, fueled by a small motor, keeps the needle pointing north even in rough seas or turbulence.
gravitational forces
water
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How is the needle of a gyrocompass initially oriented north?
with a gyroscope
with a magnetic compass
The axis of a gyrocompass is pointed north using a magnetic compass as a reference. Magnetic compasses are also periodically used to correct any errors picked up by the gyrocompass.
with a motor
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Which of the following do you not need in order to make your own compass?
a shallow dish of water
something small that floats
thick string
To make your own compass, all you have to do is place a magnetized needle on a lightweight floating material in a dish of water. The needle will slowly point toward north.
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You Got:
/10
Garry Gay/Getty Images
