Few pupils are able to use the idea of potential to explain or predict observations about simple circuits.
Misconception
In particular, students often struggle to move beyond the idea of voltage being a measure of 'strength of push' to the idea of it being a difference in some sort of 'level'.
Resources to Address This

Predicting and Measuring Voltages (1114)
Source  SPT / El03TA02
This practical activity, aimed at slightly older classes, encourages students to predict voltage measurements and associated circuit behaviour before they take measurements using a voltmeter. This can facilitate an improved understanding of the role of voltage in electric circuits.
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What do Voltages Measure? (1114)
Source  SPT / El03TL05
This resource discusses a variety of ways that teachers can use to talk about voltage to students of different ages and abilities.
Batteries of greater voltage provide a bigger push, which leads to more power dissipated in the circuits that they're a part of.
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Testing understanding adding lamps in series (1114)
Source  SPT / El02TA06
The What happens to the current? question probes the effect on the electric current of adding a bulb to a circuit.
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References
The following studies have documented this misconception:
 Küçüközer, H. and Kocakülah, S. () Effect of Simple Electric Circuits Teaching on Conceptual Change in Grade 9 Physics Course. Journal of Turkish Science Education.
 Millar, R. and King, T. () Students’ understanding of voltage in simple series electric circuits. International Journal of Science Education, 15 (3),
339349.
 Benseghir, A. and Closset, J. L. () The electrostatics‐electrokinetics transition: historical and educational difficulties. International Journal of Science Education, 18 (2),
179191.
 Lee, Y. and Law, N. () Explorations in promoting conceptual change in electrical concepts via ontological category shift. International Journal of Science Education, 23 (2),
111149.
 Guth, J. () An indepth study of two individual students' understanding of electric and magnetic fields. Research in Science Education, 25 (4),
479490.
 McDermott, L. C. and Shaffer, P. S. () Research as a guide for curriculum development: An example from introductory electricity. Part I: Investigation of student understanding. American Journal of Physics, 60 (11),
9941003.
 Cohen, R.; Eylon, B. and Ganiel, U. () Potential difference and current in simple electric circuits: A study of students’ concepts. American Journal of Physics, 51 (5),
407412.