An electrostatic sprayer gives droplets of disinfectant a negative charge. A metal hospital trolley is normally earthed by a cable while it is sprayed. During one session the cable is left unconnected, and the trolley stands on rubber wheels, so it is insulated from earth. The nozzle and the spraying rate are unchanged.
Which conclusion is most appropriate?
Landing droplets give the trolley a negative charge, so it repels later droplets and less liquid reaches it.
More liquid reaches the trolley, because an insulated metal object keeps a positive charge.
The same amount of liquid reaches the trolley, because the droplets are still negatively charged.
The droplets no longer repel one another, so they join into large drops that miss the trolley.
80 exam-style questions on Edexcel GCSE Physics 11.2 Uses, dangers and electric fields, covering 11.2.1 Uses of electrostatic charge, 11.2.2 Dangers of sparking, 11.2.3 Electric fields, and 11.2.4 Electric fields and static electricity. Each one has a worked solution and a mark scheme showing where the marks go.