Positive and Negative Charge

Five unknown charges are shown on the screen along with vectors representing the forces on each charge.  You can click-drag on any charge to change its position.  How many charges are alike? Start

Script

document.EField.setAutoRefresh(false);
document.EField.setDefault();
document.EField.setShowTime(false);
document.EField.setDrag(true);
document.EField.setShowForce(true);
document.EField.setChargeRGB(0,0,0);
document.EField.addCharge(-2,0,3);
document.EField.addCharge(2,0,-2);
document.EField.addCharge(0,2,-2);
document.EField.addCharge(0,-2,2);
document.EField.addCharge(0,0,2);
document.EField.setAutoRefresh(true);