Magnetic Effects of Current and Magnetism — Easy Practice (Set 2)

Quick Recap — Forces, Torques & Magnetism

• Force on a wire: $F = BIL\sin\theta$; parallel wires attract (same direction) or repel (opposite), with $\dfrac{F}{L} = \dfrac{\mu_0 I_1 I_2}{2\pi d}$ — this defines the ampere.
• Current loop: magnetic moment $m = NIA$; torque $\tau = mB\sin\theta = NBIA\sin\theta$.
• Galvanometer: a small parallel shunt makes an ammeter; a large series resistance makes a voltmeter.
• Bar magnet: the axial field is twice the equatorial field at the same distance, and both fall off as $1/r^3$.
• Materials: diamagnetic (weakly repelled), paramagnetic (weakly attracted) and ferromagnetic (strongly attracted; they become paramagnetic above the Curie temperature).