3. The Electromagnetic Pump. Magnetic þnducting onvenient means of pumping these fluids. For example, this method can be used to pump blood without the damage to the cells that can be caused by a mechanical pump. A horizontal tube with rectangular cross section (height h, width w) is k placed at right angles to a uniform magnetic field with magnitude B so acting provide forces on fluids а `Liquid metal or blood that length is in the field. The tube is filled with a conducting liquid, and an electric current of density J is maintained in the third mutually perpendicular direction. Show that the difference of pressure between a point in the liquid on a vertical plane through ab and a point in the liquid on another vertical plane through cd, under conditions in which the liquid is prevented from flowing, is .

1. Two straight parallel wires, running north/south are separated by 10 cm and carry currents of 3A in the same direction (north). a) Find the magnitude and direction of the magnetic field at a point midway between the wires. b) Find the magnetic field 6 cm east of the "easternmost" wire. c) Calculate the force of one wire on the other. Is it attractive or repulsive?

b) Singly-ionised atoms accelerated by a 20 kV potential enter a region with a magnetic field at right angles to the ion beam. The ion beam is deflected, so that after travelling 20 cm in the magnetic field atoms of a selected mass exit through a slit at right-angles to the input beam. Calculate the magnetic field required to select carbon-12 atoms.

nillan Learning Activity on the Sun, such as solar flares and coronal mass ejections, hurls large numbers of charged particles into space. When the particles reach Earth, they can interfere with communications and the power grid by causing electromagnetic induction. For example, a current of millions of amps (known as the auroral electrojet) that runs approximately 100 km above Earth's surface can be perturbed. The change in the current causes a change in the magnetic field it produces at Earth's surface, which induces an emf along Earth's surface and in the power grid (which is grounded). Induced electric fields as high as 6.0 V/km have been measured. We can model the circuit at Earth's surface as a rectangular loop made up of the power lines completed by a path through the ground beneath. We can treat the magnetic field created by the electrojet as being uniform (but not constant) and parallel to Earth's surface near the surface. Consider a 1.0-km-long stretch of power line that is…