Everything Science Grade 11

CHAPTER 18. ELECTROMAGNETISM 18.2

2. One student shouldbe in charge of limitingthe current flow to 10 seconds. This is to
   preserve battery life as well as to prevent overheating of the wires and battery contacts.


3. Place the compass close to the wire.


4. Close the circuit andobserve what happens to the compass.


5. Reverse the polarity of the battery and close the circuit. Observe whathappens to the
   compass.

Conclusions:

Use your observations to answer the following questions:

1. Does a current flowing in a wire generate a magnetic field?


2. Is the magnetic fieldpresent when the current is not flowing?


3. Does the direction of the magnetic field produced by a current in a wire depend on the
   direction of the currentflow?


4. How does the direction of the current affect the magnetic field?

Activity: Magnetic field around aloop of conductor

Consider two loops made from a conducting material, which carry currents (in opposite

directions) and are placed in the plane of the page. By using the Right Hand Rule, draw what

you think the magneticfield would look like atdifferent points around each of the two loops.

Loop 1 has the current flowing in a counter-clockwise direction, while loop 2 has the current

flowing in a clockwise direction.

direction of current

direction of current

loop 1

direction of current

direction of current

loop 2

If you make a loop of current carrying conductor, then the direction of the magnetic field is obtained
by applying the Right Hand Rule to different points in the loop.

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The directions of the magnetic field

around a loop of current carrying

conductor with the current flowing

in a counter-clockwise direction is

shown.

If we now add another loop with the current inthe same direction, thenthe magnetic field around
each loop can be addedtogether to create a stronger magnetic field. A coil of many such loops is
called a solenoid. The magnetic field pattern around a solenoid is similar to the magneticfield pattern
around the bar magnet that you studied in Grade 10, which had a definite north and south pole.