Magnetic Field Around a Loop of Wire
Using current and the left-hand rule to predict the field of a current loop
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"My Magnet Attracting Money"
'Did you know that US currency is attracted to a magnet? There are iron
particles in the ink that is causes this attraction.'
Rob Gallagher
Making a Magnet Electric Magnets are created using
We can understand an electric magnet
Ex 3) Magnetic field around a Single Loop of Wire w/ current
A loop of wire with current
North Pole is either
Finding N. and S. Pole
Step 1 - Current travels from (-) to (+) terminal, DRAW
the direction of the current on the wire
Step 2 - Palms away, thumb in direction
of current
Step 3 - Curl fingers of left hand into loop Why Left and not right??
Step 4 - Note where four fingers tips are
pointing when they enter the INSIDE
of the loop
Fingers tips - NORTH POLE of the magnetic field
North Pole
Below
South Pole??
Above
North Pole
Below
North Pole
Above
South Pole
Below
If (+) and (-) terminals are reversed
Magnetic Poles?
Poles are reversed
Using magnets to
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Check Your Understanding
5 quick questions — pick an answer to see if you’re right.
1. A single loop of wire carrying current acts like:
2. In the left-hand rule for a loop, the fingertips point into the inside of the loop. Where they point is the:
3. A loop lies flat on a table. Viewed from above, electron current flows clockwise. Where is the north pole?
4. The battery's (+) and (−) terminals connected to a loop are switched. What happens to the loop's magnetic poles?
5. A strong magnet can pick up a US dollar bill. Why?
The Magnetic Field of a Current Loop
A student bends a wire into a single circular loop, connects it to a battery, and uses small compasses to map the magnetic field around and through the loop.
Which statement best describes the field of the current loop?
▶ Want a challenge? Open 6 more Regents-style questions (harder · mixed formats)
Challenge score: 0 / 6
C1. A student makes the following claim.
Place a check mark in either the Support or Refute box. Justify your response.
C2. The current in the loop is reversed. What happens to the field?
C3. The loop is set up so its axis points north–south (north is toward the top of the page). At the center of the loop, the loop’s field is 5.0 × 10−5 T directed south, and Earth’s horizontal field is 2.0 × 10−5 T directed north. Choose the direction of the net magnetic field at the center, and determine its magnitude.
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C4. Place a check mark in three boxes to indicate the changes that would make the magnetic field at the center of the loop stronger.
C5. What does a straight current-carrying wire produce around itself?
C6. A student wants to build a sensitive current detector by winding wire into a coil around a compass. Identify one benefit and one drawback of using many more turns of wire in the coil.