/* @GuardedBy("this") */
	synchronized double getKEOfElectrons() {
		if (freeElectrons.isEmpty())
			return 0;
		double x = 0;
		synchronized (freeElectrons) {
			for (Electron e : freeElectrons) {
				x += (e.vx * e.vx + e.vy * e.vy) * Electron.mass;
			}
		}
		return x * EV_CONVERTER / freeElectrons.size();
	}