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I am currently studying Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk. Chapter 2.5 Resistance, Resistivity, and Conductivity presents the following image (without description) when discussing the concept of resistance:

enter image description here

I have the following questions:

  1. What does the \$ A \$ symbol pointing to the left-hand-side of the Ohmic material represent?
  2. What does the arrow going through the battery symbol represent?

I would appreciate it if people would please take the time to clarify this.

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    \$\begingroup\$ It's a battery of archers! \$\endgroup\$ – Hot Licks Jan 26 at 3:45
  • \$\begingroup\$ @HotLicks No, it's a archer cell. There's only one. \$\endgroup\$ – DKNguyen Mar 18 at 23:05
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A is the cross sectional area of the resistor.

The arrow through the voltage source indicates its voltage is variable. The device is likely not actually a battery because a variable battery is not an easily realizable device.

An arrow through a component is a common indicator for a variable value; for example you'll see variable resistors and variable capacitors indicated this way also.

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    \$\begingroup\$ In general an arrow going diagonally through any component indicates that it is variable -- although a "variable battery" is an odd concept. Probably the author is playing fast and loose with the nomenclature, and just means "voltage source" when they write a battery symbol. \$\endgroup\$ – TimWescott Jan 25 at 17:02
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    \$\begingroup\$ Often found in physics textbooks, number one source of confused electronics novices asking for variable batteries in even more confused stores. BTW, an arrow through any kind of real battery is a BAD idea :) \$\endgroup\$ – rackandboneman Jan 26 at 1:40

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