Current

Conventional current is defined as positive-charge flow, even though electrons (negative) are the actual movers in most circuits.
Current: I = Q/Δt, measured in amperes (A) = 1 C/s.
DC (constant direction) is what the MCAT tests; AC (periodically reversing direction) is not tested.
Voltage drives current; emf is the energy per unit charge a source supplies, present even with no current flowing (open circuit).
Kirchhoff's Junction Rule (Iin = Iout, conservation of charge) and Loop Rule (Vsource = Vdrop, conservation of energy) let you analyze any circuit.

I = Q/Δt

Rule	Statement
Junction Rule	Iin = Iout at any junction (conservation of charge)
Loop Rule	Vsource = Vdrop around any closed loop (conservation of energy)

Direct Current (DC)	Alternating Current (AC)
Constant direction	Direction reverses periodically
Constant voltage over time	Sinusoidal voltage over time
Batteries, flashlights, phones	Generators, power grids
MCAT-tested	Not MCAT-tested

Conventional current direction is opposite to actual electron flow — don't assume electrons move 'with' the current arrow.
emf is not actually a force despite the name — it's energy per unit charge (volts), and it exists even in an open circuit with zero current.

3 A enters a junction and splits into two branches; one carries 1 A. What does the other carry?

Why does emf exist even when no current is flowing?

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