Electric Charge, Current and Voltage flashcards

By gaining or losing electrons. Extra electrons give a net negative charge; missing electrons leave a net positive charge. Protons do not move. Like charges repel, unlike charges attract, and total charge is conserved.

$I=\frac{Q}{t}$: current in amperes equals charge in coulombs divided by time in seconds. 1 A = 1 C/s. Example: 30 C in 6 s is 5 A.

$V=\frac{E}{Q}$: potential difference in volts equals energy in joules per coulomb of charge. 1 V = 1 J/C. A source giving 54 J to 6 C is 9 V.

Conventional current flows from the positive terminal through the load to the negative terminal. Electrons in a metal wire drift the opposite way, negative to positive. Use conventional current unless electron flow is named.

Ammeter: in series, inside the loop, so the current passes through it (nearly zero resistance). Voltmeter: across the component, in parallel (very high resistance). An ammeter across a battery acts as a near short circuit.

Milli (m) divide by 1,000: 750 mA = 0.75 A. Micro ($\mu$) divide by 1,000,000: 40 $\mu$A = 0.00004 A. Kilo (k) multiply by 1,000: 4.7 k$\Omega$ = 4,700 $\Omega$.

No, it is charge: 1 Ah = 1 A for 3,600 s = 3,600 C, so 2 Ah = 7,200 C. Energy also requires the voltage; equal Ah at 12 V holds eight times the energy of 1.5 V.

No. In an unbranched loop the current is the same at every point; the lamp converts energy, not charge. Opening a switch stops current everywhere, but the battery voltage still appears across the gap.