# Magnetism Chapter 19 Magnetism Section 2 Magnetism from

• Slides: 8

Magnetism Chapter 19 Magnetism Section 2 Magnetism from Electricity © Houghton Mifflin Harcourt Publishing Company Section 1

Magnetism Section 2 What do you think? • Electromagnets are used every day to operate doorbells and to lift heavy objects in scrap yards. • Why is the prefix electro- used to describe these magnets? • Is electricity involved in their operation or do they create electricity? • Would such a magnet require the use of direct current or alternating current? • Why? © Houghton Mifflin Harcourt Publishing Company

Magnetism from Electricity • A compass needle held near a current carrying wire will be deflected. – Electric current must produce a magnetic field. – Discovered by Hans Christian Oersted • Many compasses placed around a vertical current carrying wire align in a circle around the wire. © Houghton Mifflin Harcourt Publishing Company Section 2

Magnetism Section 2 Right-Hand Rule • To find the direction of the magnetic field (B) produced by a current (I): – Point your right thumb in the direction of the current – Curl your fingers and they will show the direction of the circular field around the wire. © Houghton Mifflin Harcourt Publishing Company

Magnetism Section 2 Magnetic Fields C B A © Houghton Mifflin Harcourt Publishing Company • Use the right hand rule to decide what direction the magnetic field would be at points A, B, and C. • Since magnetic fields are vectors, how would the net field appear in the center of the loop?

Magnetism Section 2 Magnetic Field of a Current Loop Click below to watch the Visual Concept © Houghton Mifflin Harcourt Publishing Company

Magnetism Section 2 Magnetic Field Around a Current Loop • Magnets and loops of wire have magnetic fields that are similar. • Solenoids are coils of wire similar to the single loop. – More loops strengthens the field – Placing an iron rod in the center strengthens the field as well • Called an electromagnet © Houghton Mifflin Harcourt Publishing Company

Magnetism Section 2 Now what do you think? • Electromagnets are used every day to operate doorbells and to lift heavy objects in scrap yards. – Why is the prefix electro- used to describe these magnets? • Is electricity involved in their operation or do they create electricity? – Would such a magnet require the use of direct current or alternating current? • Why? © Houghton Mifflin Harcourt Publishing Company