Physic Labs

Electricity and magnetism

Electric potential and voltage

Explore the uniform field between parallel plates to measure E=∣ΔV∣/dE = |\Delta V|/d and track a test charge’s potential energy U=qV(x)U = qV(x) with position.

High school

Equipment

  • Virtual pair of parallel plates held at +V and 0 V
  • Sliders “Hiệu điện thế” (voltage), “Khoảng cách bản” (plate gap), “Điện tích thử” (test charge)
  • Slider “Vị trí của điện tích” (charge position) on the energy graph
  • 3D canvas showing equipotential planes and field arrows, with the E readout line

Procedure

  1. Measure the field strength between the plates

    In figure 1, set «Hiệu điện thế» to 50 V and drag «Khoảng cách bản» from 0.30 m to 1.00 m. Read the line “E = |ΔV|/d = …” and record E at two gaps; verify E=∣ΔV∣/dE = |\Delta V|/d and note that the equipotential planes stay parallel and perpendicular to the field arrows. Drag the canvas to rotate and view the planes from other angles.

  2. Track potential energy with position

    In figure 2, slide «Vị trí của điện tích» from 0% to 100% and read “U = qV = …”; the U(x) graph falls linearly from the + plate to the 0 V plate. Change «Điện tích thử» from 2 nC to 5 nC and compare: potential energy scales with charge via U=qVU = qV, while V(x) is unchanged because it is set by the field alone.

  3. Note the field direction and predict

    Observe the field arrows running from the +V plate to the 0 V plate: a free positive charge would move that way, losing potential energy and gaining kinetic energy. Before changing «Hiệu điện thế» to 100 V, predict E at the current gap, then check the readout; compare your prediction with E=∣ΔV∣/dE = |\Delta V|/d.

Simulation

Experiment history

Around 1780 Luigi Galvani observed frog legs twitching when touched by two different metals; Alessandro Volta argued the effect came from the metals, not from animal tissue. In 1800 Volta announced his pile of zinc and copper discs separated by brine-soaked cloth — the first source maintaining a sustained potential difference — and the unit volt was later named for him. The notion of electric potential matured through the nineteenth century as physicists sought to describe energy independently of the charge used to measure it. In his Experimental Researches in Electricity, Michael Faraday described electric fields and lines of force around charged bodies, noting that the field points from high to low potential — the ancestor of the relation E=∣ΔV∣/dE = |\Delta V|/d for a uniform field between parallel plates. James Clerk Maxwell later cast these observations into mathematical form in A Treatise on Electricity and Magnetism (1873), making potential and field two equivalent views of the same electrostatic system.

Related physicists

Charles-Augustin de CoulombJames Clerk MaxwellMichael Faraday

Related library topics

Electric potential and voltage