# Why do charges repel like magnets?

## Physics Sexl 6 RG, textbook

Experiment: Magnetism 82.1 You need: Permanent magnets, coil, voltage source, iron filings, iron nails E 1 a) Investigate the effect of permanent magnets on iron, steel and other metals. Examine the deflection of magnetic needles near a permanent magnet. Describe your observations. E 1 b) Investigate the magnetic effect of the electric current. Pass current through a wire coil with about 100 turns and observe its effect on iron nails or iron filings. Describe your observations. The current-carrying coil attracts iron nails like a magnet. The magnetic effect is propagated into the iron nails. They are magnetized and have a “north pole” pointing north and a corresponding “south pole”. Steel nails retain their magnetization, soft iron nails lose them again when the power is switched off. Magnets act on one another in a similar way to electrical charges: Magnetic poles with the same name repel one another, while those with different names attract one another. Pointer measuring devices (so-called analog measuring devices) for the electrical current strength use the magnetic effect of the current. The functional principle is easy to understand on the moving coil measuring device (82.1). The current to be measured flows through a light, rotatable coil. The current makes the coil magnetic and an external magnet generates a torque. The spool rotates until a spiral spring exerts an oppositely equal torque. The deflection of the needle on the coil indicates the strength of the current. Analog measuring devices make it easy to see a change in the display, while the exact value of the current is not so easy to read. Today mostly digital measuring devices are used, which display the measured value in digits. Magnetic forces between electrical currents Teacher's experiment: Force between current-carrying conductors 82.2 Observe and describe how two parallel current conductors behave when electrical currents flow through them in the same or opposite direction. Try an explanation. The French physicist A NDRÉ -MARIE A MPÈRE (1775–1836) learned of Oersted's discovery. As early as the autumn of 1820 he discovered the magnetic force between two parallel conductors carrying current: mutual attraction with the same direction of current, repulsion with opposite direction of current. The current definition of the unit of electrical current is based on this effect (see p. 109). c Conducting electricity in liquids - the chemical effect Experiment: Conducting electricity in liquids 82.3 You need: vessel, 2 electrodes (metal plates), adjustable power supply, ammeter, supply lines, distilled water, tap water, table salt, vinegar. E 1 a) Set up an experiment as in 82.2. Connect the poles of the voltage source with metal electrodes that you hang one after the other in different liquids (distilled water, tap water, salt water, diluted vinegar). Apply different voltages (up to a maximum of 12V) to the electrodes. Measure voltage and amperage and display the data graphically. E 1 b) Transfer the measurement data to a graph. Interpret the result. 82.3 A NDRÈ -MARIE A MPÈRE (1775 Lyon - 1836 Marseille) was interested in philosophy, mathematics and the natural sciences from an early age. He studied probability theory and taught physics in Lyon before becoming a member of the French Academy of Sciences at the age of 30. His investigations into electromagnetism led him to the hypothesis that magnetism is always caused by currents. Scale Pointer Power supply Coil N S Permanent magnet Iron core 82.1 Moving coil measuring device. When there is electricity, the coil becomes an electromagnet, it is rotated by the permanent magnet. 82.2 Electrolysis Experiment 82 E-LEARNING For testing purposes only - property of the publisher öbv