Chapter 45 · 1,095 practice MCQs
MDCAT Current Electricity MCQs 2026 | Ohm, r, Max Power
Current is charge per second, not a fluid of voltage. Unit 9 is , Ohm, resistivity, internal resistance and maximum power when — a curve, not a slogan.
·6 min read·Usman Ubaid
What MDCAT 2026 asks in Unit 45 Current Electricity
PMDC Unit 9 is the practical-bench chapter. Current Ohm’s law holds for ohmic metals at steady temperature; a filament is not ohmic. Resistance double the length, double R; double the diameter, R falls by four.
A real cell is emf E plus a little internal r. Terminal voltage − Ir. Open circuit: Short circuit: Power in the load peaks when — too small a load dumps power in r; too large a load starves the current.
Twenty practical labs: Ohm, resistivity, the P–R curve, shorts and opens.
- Conventional current is the direction a + would flow.
- Ohm: for ohmic conductors. Graph through the origin, constant slope.
- Diameter ÷4.
- − Ir. Terminal voltage falls as current rises.
- is maximum at Matching is a peak on a curve.
Often-asked Current Electricity MCQ patterns
These are the Current Electricity ideas that keep coming every year with new numbers.
- Forgetting r when the current is large.
- Saying maximum power is at (that is a short; power in the load is zero).
- Using the open-circuit voltage as the loaded voltage.
- Resistivity changing with length — is a material, R is the object.
Worked Current Electricity numericals (
Work these on paper first. Then open the Unit 45 quiz — the same numbers are in the questions, with wrong options built from the usual mix-ups.
A wire’s diameter is doubled, length the same. New resistance?
Resistance falls to one quarter. Diameter, not radius, was the stem — still a square in the area.
A cell V, . Load for maximum power, and that power?
Match R to r. in the load; an equal is wasted in r.
Current Electricity traps that steal the mark
A good option is a true sentence about the wrong quantity. If you miss, the quiz names the mix-up on the option you actually picked.
- Forgetting r when the current is large.
- Saying maximum power is at
- Using the open-circuit voltage as the loaded voltage.
- Treating a filament as ohmic.
- Scaling R with diameter instead of diameter squared.
Current Electricity formula sheet for MDCAT 2026
Write these until they are cheaper than thinking. Then open the Current Electricity quiz and make the picture agree.
- at
How to practise Unit 45 Current Electricity MCQs
On a cell question, write a loop: + r) before you name V. Terminal voltage is what is left after Ir.
On a power question, sketch P against R in your head: zero at , zero as R → ∞, peak at
Sit Current Electricity after Electrostatics and before Electromagnetism.
Choose topics and a test length up to 180 from the 1,095-question bank. Tutor Mode explains each selection; Timed Exam reveals explanations on submission. Use the complete review to revise mistakes and download your results.
FAQ
Common questions
Why does power peak at
Too small a load dumps power in r. Too large a load starves the current. The product IV for the load is biggest when they match. Maximum load power does not mean maximum efficiency. At , half the source power is lost in internal resistance; a larger load resistance improves efficiency while reducing delivered power.
What is terminal voltage in MDCAT?
− Ir, the voltage across the load. Open circuit short circuit For a discharging cell the internal resistance causes the Ir drop. If the cell is being charged, the terminal-voltage relation changes sign, so inspect the current direction rather than using one expression automatically.
How does resistance change if diameter doubles?
Area quadruples, so R falls to one quarter (length fixed). Students who double r instead of d still get the same square. assumes the material, temperature and length remain unchanged. Since , doubling diameter multiplies area by four and divides resistance by four.
Is a light-bulb filament ohmic?
No. R rises with temperature, so I–V is not a straight line through the origin. A filament heats as current rises, changing resistivity. A metal wire approximately obeys Ohm's law only when its temperature and other physical conditions stay constant.
How many Current Electricity MCQs are available on DIFF. MDCAT?
The current Current Electricity question bank contains 1,095 practice MCQs across 9 topics. This is the bank size, not the length of one test. Choose your topics and a question count from 1 to 180, limited by the questions available in those topics.
Which topics does the Current Electricity quiz cover?
The selectable topics are Electric Current, Ohm's Law, Resistivity, Internal Resistance, Maximum Power, Steady current, Power transfer, Ohm's law, Internal resistance. Use Select all for a broad chapter drill, Clear to start a focused selection, or choose individual topics. Questions are drawn from your chosen topics, so you can target a weak concept before returning to a wider test.
How do I build a custom Current Electricity test?
Open the chapter builder, select one or more topics, enter your question count, and choose Tutor Mode or Timed Exam. The available-question total updates with your selection. Start Test generates a shuffled drill; you do not have to follow a fixed Quiz 1 or Quiz 2 sequence.
What is the difference between Tutor Mode and Timed Exam?
Tutor Mode gives feedback and an explanation after you choose an option, and you can change or clear that choice. Timed Exam runs a countdown and keeps explanations hidden until submission. Both modes let you move between questions, use the paper map, and submit for a complete review.
How do I review and download my Current Electricity quiz?
Select Submit Quiz, then Submit & View Explanations. The review includes every question in your test, all options, your selection, the marked correct answer when a key is available, and the explanation. Download PDF saves a paginated review; Download Review saves an HTML copy you can open in a browser. The review also includes DIFF. MDCAT community links.
How should I use Current Electricity MCQs to improve?
Start with a short tutor drill on one of these topics: Electric Current, Ohm's Law, Resistivity. Read the explanation for incorrect and uncertain answers, revise the relevant textbook section, and retry before taking a timed drill. Compare your reasoning with the answer key rather than memorising the option letter.
Ready to sit Unit 45 Current Electricity — 1095 MCQs, 1095 labs?