1. what is the si unit of emf? 2.a complete series circuit consists of a 12.0 v battery, a 4.70 ω resistor, and a switch in the closed position. the internal resistance of the battery is 0.30 ω. what does an ideal voltmeter read when placed across the resistor?

1. The volt is the derived SI unit for EMF that has been given a special name. It is equivalent to a watt per ampere, where the watt, too, is a derived unit.

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2. Total circuit resistance is 4.7Ω + 0.3Ω = 5.0Ω, so the circuit current is ...

  (12 V)/(5.0 Ω) = 2.4 A

Then the voltage across the resistor is ...

... (2.4 A)×(4.7 Ω) = 11.28 V ≈ 11.3 V

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Comment on Ohm's Law

I've found the attached diagram to be helpful for remembering the relationships involved in Ohms Law. If you cover the letter of the variable you want to find, the other two show you how to find it.

V = I×R

I = V/R

R = V/I

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)