if they're not then the circuit will not work and it won't be able to power wat u want it to power for example a lightbulb.it will be an open circuit
They can, but not required.
To carry elections
Advantages in electric circuits : Advantages of using the rheostat in electric circuits is optional as you could just use the dial on the power-supply to vary the voltage (p.d.), and therefore the current. The advantage of using the rheostat is that you can control it to give you nice even numbers for the voltage.
shock risk
series
Colin D. Simpson has written: 'Principles of DC/AC circuits' -- subject(s): Electronic circuits 'Introduction to Electric Circuits and Machines' -- subject(s): Electric circuit analysis, Electric circuits, Electric machinery 'Industrial electronics' -- subject(s): Industrial electronics
J. Richard Johnson has written: 'Electric circuits' -- subject(s): Electric circuits
Edward Nicholas Pink has written: 'The electric and magnetic circuits' -- subject(s): Electric circuits, Electric currents, Magnetism
Sadly no...
Battery
yes
They can, but not required.
It makes the current bigger
Roland E. Thomas has written: 'The analysis and design of linear circuits' -- subject(s): Linear Electric circuits, Electric circuit analysis, TECHNOLOGY & ENGINEERING / Electronics / Circuits / General, Design and construction 'Solutions manual to accompany Circuits and Signals' 'Circuits and signals' -- subject(s): Interface circuits, Linear integrated circuits
Thomas S. Kubala has written: 'Electricity One' 'Electricity' 'Electricity 1' -- subject(s): Electrical engineering, Direct current, Electric circuits, Electric machinery 'Electricity 2' -- subject(s): Electrical engineering, Electric circuits, Alternating current 'Electricity One Devices Circuits, Materials' 'Circuit concepts' -- subject(s): Electric circuits
John Douglas Ryder has written: 'Networks, lines, and fields' -- subject(s): Electric circuits, Lending library, Wave guides 'Introduction to circuit analysis' -- subject(s): Electric circuits, Electric networks 'Electronic circuits and systems' -- subject(s): Electronic circuits, Electronics, Semiconductors
Impressionist paintings are a non-example of electric circuits.