Question F.1: (a) Determine the current (I) in the circuit of Figure F–1 i......
(a) Determine the current (I) in the circuit of Figure F–1 if V = 10 V and R = 2 Ω.
(b) Recalculate the current if R = 4 Ω.
(c) Describe what happened to the value of the current when the resistance doubled to 4 Ω in (b).
(d) Calculate the voltage required in Figure F–1 to make 2 A flow if R = 10 Ω.
(e) What voltage would be required in (d) if you only need one-half that current?
(f) If V = 12 V in Figure F–1, what resistance is required to limit the current to 2 A?
(g) To limit the current to 1 A in (f), what resistance would you need?
(a) I={\frac{V}{R}}={\frac{10\,\mathrm{V}}{2\,\Omega}}=\,5\,\mathrm{A}
(b) I={\frac{V}{R}}={\frac{10\,\mathrm{V}}{4\,\Omega}}=\,2.5\,\mathrm{A}
(c) As the resistance to current flow doubled, the current dropped to one-half.
(d) V = I × R = 2 A × 10 Ω = 20 V
(e) V = I × R = 1 A × 10 Ω = 10 V
Note we only need one-half the voltage to get one-half the current.
(f) R={\frac{V}{I}}={\frac{12\,\mathrm{V}}{2\,\mathrm{A}}}=6\,\Omega
(g) R={\frac{V}{I}}={\frac{12\,\mathrm{V}}{1\,\mathrm{A}}}=12\,\Omega
Note that, to reduce the current to 1 A, we needed to increase the circuit’s resistance.