Voltage Voyage

Circuit Given

Practice question

Draw the schematic diagram on the mat, choose the circuit type, then press Diagram complete. Then find V, I and R for each load and for the whole circuit.

Drag symbols onto the mat. Choose Wire, then drag from one end point to another; wires snap to the grid. Rotate the selected symbol with ← → ↑ ↓ or by dragging its round handle. Double-click a wire to flip its corner, or a switch to open or close it. Delete removes the selection, W picks the wire tool and Esc returns to Select.

Formula triangles

Ohm's law triangle

V = I × R
I = V ÷ R
R = V ÷ I

The power triangle

P = I × V
I = P ÷ V
V = P ÷ I

Electrical power and energy triangle

E = P × t
P = E ÷ t
t = E ÷ P

Cover the quantity you want; the two left show the operation. Energy is in joules (J) when power is in watts (W) and time in seconds (s), or in kilowatt-hours (kWh) when power is in kW and time in hours.

Series and parallel relationships

Series circuit (one path)
Voltage	V_T = V₁ + V₂ + … + V_n
Current	I_T = I₁ = I₂ = … = I_n
Resistance	R_T = R₁ + R₂ + … + R_n
Parallel circuit (branches)
Voltage	V_T = V₁ = V₂ = … = V_n
Current	I_T = I₁ + I₂ + … + I_n
Resistance	1/R_T = 1/R₁ + 1/R₂ + … + 1/R_n

In parallel, R_T is always smaller than the smallest branch resistance. In series, adding a load increases R_T and lowers the current.

Solve the circuit