The most common form of magical control, the Physical magician's source of power is the energy within and around him. This energy cannot be created or destroyed, merely transferred.
As a physical adept, you feel a great well of power coursing within you. You feel static on your skin; the very air touching you is charged with potential. You can control this flow of energy, directing it around your body at will. Concentrating the magical force in your muscles grants inhuman strength and speed. Direct the flow to your fists, and they become cloaked with crackling energy.
As a physical caster, the fabric of your surroundings is an extension of your own arm. Within a several metre radius, you can feel the pulsations of the environment. You can draw the energy around you into a single point, much like drawing a bow, and prepare to release. What form it takes depends on your will, be it a bolt of lightning or shards of ice.