FOCUSED REVIEW
Focused Review — Current, Resistance, and Ohm's Law — Foundational
Reinforce the highest-leverage ideas and representative problem-solving tools for Current, Resistance, and Ohm's Law.
TIME
Approximately 15 minutes
BEST FOR
Targeted reinforcement
FINISH WITH
A readiness check
After this focused review, you'll be able to...
reinforce the key relationships, apply them to representative problems, and identify what still needs work.
Choose how you want to review
Course Alignment
This Physics Sensei Unit Review is an independent learning resource. Use it to reinforce key concepts, prepare for homework, or review before a quiz or exam.
RESOURCE: Physics Sensei Unit Review | UNIT ID: EME-U06 | TOPIC: Current, Resistance, and Ohm's Law | COURSE LEVEL: Foundational
BEST USED ✓ After learning the unit ✓ Before starting homework ✓ Before a quiz or exam
Your Review Plan
Complete these six stages in order. Each stage builds on the previous one and prepares you for the final readiness check.
6 Stages • Approximately 15 minutes.
Warm-Up Check
Before you begin, take a moment to see what you already remember. Do not worry about getting everything right. This is only a starting point.
ACTIVITY 1
Name the moving quantity
Work through the question, then check your reasoning.
What physical quantity must move across a cross-section for electric current to exist?
Reveal Answers
Electric charge moves; in a metal, the mobile carriers are electrons.
Why it works: Current requires transport of electric charge across a surface, rather than motion of energy or voltage. Metals contain mobile electrons that carry this charge through the wire.
ACTIVITY 2
Separate current and voltage
Work through the question, then check your reasoning.
Explain why a battery can have a voltage even if the switch is open.
Reveal Answers
The open switch interrupts a conducting path; the battery still provides a potential difference.
Why it works: A battery maintains a potential difference between its terminals even when no continuous conducting path exists. Opening the switch stops sustained current, not the separation of potential at the terminals.
ACTIVITY 3
Direction check
Work through the question, then check your reasoning.
Electrons drift left in a metal wire. Which way is conventional current?
Reveal Answers
Conventional current is rightward, opposite leftward electron drift.
Why it works: The direction assigned to conventional current is the direction a positive charge would move. Because electrons carry negative charge, leftward electron drift corresponds to rightward conventional current.
Ready to strengthen your understanding?
You've refreshed what you already know. Next, you'll reinforce the essential concepts that will help you solve problems with confidence. Need to see the learning path again?
Core Concepts
Reinforce the two highest-leverage relationships, then use them in representative situations.
KEY CONCEPT 1
What current means
Electric current is the rate at which electric charge crosses a chosen surface. Conventional current points in the direction positive charge would move. In metal wires, electrons drift in the opposite direction.
Example: A lamp can carry a steady current even though individual electrons drift slowly.
Sensei note: Do not confuse conventional current direction with electron motion.
KEY CONCEPT 2
Voltage, resistance, and Ohm’s law
Potential difference is energy transferred per unit charge. Resistance describes how strongly a component opposes current. For an ohmic component at constant conditions, V = I R.
Example: At the same resistance, doubling the applied voltage doubles the current.
Sensei note: V = I R is not a universal law for every device: a filament bulb may be non-ohmic.
Ready to apply these ideas?
You've reinforced the essential concepts. Now it's time to put them into practice by working through guided examples and building your problem-solving confidence. Need a quick reminder?
Guided Practice
Apply the reinforced ideas to two representative situations, then use the strategy card to check your setup.
PRACTICE 1
Battery and lamp
Work through the question, then check your reasoning.
A 6 V battery is connected across an ohmic 3 Ω lamp. Determine current and identify the relationship used.
Reveal Answers
I = V/R = (6 V)/(3 Ω) = 2 A. Use Ohm’s law because resistance is specified and constant.
Why it works: For a component whose resistance is treated as constant, Ohm’s law relates the potential difference and current by V = IR. Dividing 6 V by 3 Ω gives 2 A; this assumes the lamp is behaving ohmically under the stated conditions.
PRACTICE 2
Power check
Work through the question, then check your reasoning.
A device has a 12 V potential difference and carries 0.5 A. Find its power.
Reveal Answers
P = I V = (0.5 A)(12 V) = 6 W.
Why it works: Electrical power is the rate of energy transfer. Each coulomb transfers 12 J at 12 V, and 0.5 C crosses per second, so the energy transferred per second is (12 J/C)(0.5 C/s) = 6 W.
Ready to check your understanding?
You've practiced the essential skills with guidance. Now it's time to solve a few short problems on your own and confirm you're ready to move forward. Need a quick reminder?
Confidence Check
You've rebuilt the key ideas and practiced them with guidance. Now try these short questions on your own to check your understanding before moving on.
QUICK CHECK 1
Current direction
Work through the question, then check your reasoning.
In a copper wire electrons move to the right. State the conventional current direction.
Reveal Answers
Left; conventional current follows positive charge.
Why it works: Conventional current is defined by the motion positive charge would have, so it points opposite the electron drift direction in a metal conductor.
QUICK CHECK 2
Resistance effect
Work through the question, then check your reasoning.
An ohmic resistor is held at 8 V. Its resistance doubles. What happens to the current?
Reveal Answers
It halves because I = V/R.
Why it works: For fixed voltage across an ohmic resistor, I = V/R makes current inversely proportional to resistance. Doubling R while keeping V unchanged halves I.
How did it go?
You've checked your understanding. Take one final look at the essential ideas before deciding what to do next. Need a quick reminder?
Summary
Before moving on, take one final look at the most important ideas from this review.
KEY TAKEAWAY 1
Current
Current measures charge flow per unit time; conventional current is opposite electron drift in metals.
KEY TAKEAWAY 2
Ohm’s law
For an ohmic resistor at fixed temperature, V = I R.
Ready for your next step?
You've reviewed the essential ideas one last time. Now choose the resource that best matches how confident you feel. Need a quick reminder?
Next Step
Great work!
You've completed this review. Choose the next resource that best matches how confident you feel.
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Review the key ideas and examples again.
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