System of Units
- Systeme International (SI)
- 7 base units: kilogram, meter, second, ampere, kelvin, candela, mole
- Derived units
Electrical Forces and Fields
• Charge measured in Coulomb (C)
• F = kq1q2/r2
• with q1 and q2 charges, r the distance between
• charges, and k a constant
• E = F/q
• Electrical Forces on Charge, F = E
Electrical Current
• SI unit ampere
• I = q/t
Electrical Potential Difference
Electrical Potential Difference
• Voltage: V = E / q measured in volt (V)
with E the electrical potential energy in joule (J)
with E the electrical potential energy in joule (J)
• 1 volt = 1 joule per coulomb
• Electron-volt (eV): Kinetic energy obtained by an electron accelerated across potential difference of one volt
• 1 eV = 1.602 Í 10-19 J
Electrical Power
• SI unit – watt (W)
• 1W = 1 joule per second
• P = VI
Direct and Alternating Current
• Normal household use single phase 220 V AC
Conductors
• Resistance
• R = V/I or V = IR
• Ohm’s Law
• SI unit ohm (W)
Magnetic Forces and Fields
• Magnetic fields caused by moving electrical charges
• Two poles: North and South
• Magnetic dipole
Magnetic Forces and Fields
• SI unit, magnetic field strength, tesla (T)
Electromagnetic Induction
• Michael Faraday
• Changing magnetic field induces PD
• Lenz’s Law: magnetic field opposes the inducing field
Electromagnetic Induction
Electromagnetic Induction
• Self Induction
• Mutual Induction
Magnetic Properties of Matter
• Diamagnetic Materials
• Individual electrons orbiting nucleus give rise to magnetic fields too small to measure
• Paramagnetic Materials
• Ferromagnetic Materials
• Iron, nickel and cobalt
• Magnetic Domains
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