Direct current circuits
41 important questions on Direct current circuits
How is the potential difference calculated for series components?
- Total pd = sum of pds across each component.
- In Figure 3: V0 = V1 + V2 + V3.
What rule applies to potential difference in parallel circuits?
- Pd across components in parallel = the same.
- Example: each gets 4V if the total is 8V.
What are the rules for potential differences in circuits?
- Series: Total pd = sum across components.
- Parallel: Pd is equal across components.
- Higher grades + faster learning
- Never study anything twice
- 100% sure, 100% understanding
For my 1st exam, I got a C. Then, I started looking for ways to learn better, and I came across Study Smart. Since then, I have scored an A+, A, A-, and another A. I highly recommend it to everyone who wants to hear it. I am so happy with it!!
I was struggling to finish all my first-year subjects for three years. Then I discovered Study Smart, which helped me to complete all of them within three months.
Because of StudySmart, things are going well in many ways. Before, I always had study stress and no time for anything. Now I feel calm and confident (because of the program). I used to score a B, and now I usually score an A or A+.
Hey Chris, I really want to thank you very much for developing the platform, I usually got around C for my exams, now I scored an A+, an A and a A- !!
Since using Study Smart, my average has increased significantly. I even completed a statistics course with an A+ while I'm bad at statistics. I took on extra classes this year because of Study Smart. Thanks so much!
Ever since I started studying with StudySmart, I have passed all my exams! No more re-sits! At first, I was happy with a pass, and now I only get good grades. Many thanks!
I aced all the courses I studied with Study Smart. For law, I first scored a D, and now an A! I’m 100% sure that I’ll pass all the courses I study with Study Smart.
I always thought I studied well. My grades were fine. I could never have imagined that applying these study skills would have such a huge and direct impact on each stage, my speed, and the pleasure I have in learning.
For the first time, I finally feel confident about the way I learn. I have the perfect overview and have made significant progress in terms of speed and the grades I get. Thanks, Chris!
I immediately started to enjoy learning again, and my grades soared. All of a sudden, everything went better. I highly recommend Study Smart to all students..
Being able to create my materials online made the process of studying so much smoother and quicker. I no longer have to spend a considerable amount of my time developing my summaries.
At first, my notes were a mess. Now I use Study Smart to take my notes in a perfectly structured way. It helps me to save a lot of time and do other things I enjoy.
Students that study with Study Smart get better grades. The system applies all the learning methods so that both well-performing students and students who struggle perform much better.
Hi Chris, I would like to thank you very much. Last year I scored C on a course, and this year I got an A+ thanks to your method! Thank you very much!
The most considerable effect is that my child is more enthusiastic about school! Every parent wants their children to be happy at school. Study Smart made it happen.
In high school, I failed several exams, and that has really changed now. I actually needed this tool very much back then. Since I started studying with StudySmart, I haven't had any Ds. My average score is now an A, and those are results I would have never had in the past.
With my old method, I passed only 3 out of 8 courses. However, since I started taking my notes digitally in Study Smart, I have passed all my lessons on the first try. For me, StudySmart takes away the stress of wondering if I will give or not.
Thanks to StudySmart, I passed all my exams and with better grades than before! On top of that, I have mastered a perfect study method now, which I am confident will help me earn my degree.
How do you calculate the total resistance \( R \) for resistors in parallel?
- Use the formula:
- 1 / R = 1 / R1 + 1 / R2 + 1 / R3 + ...
- Cancellation leads to specific equations.
What does the loop rule state about emf and potential drops?
- Sum of emfs equals sum of potential drops.
- Follows from conservation of energy.
- Considers both variable resistor and light bulb.
What is internal resistance?
- Opposes electron flow in a source.
- Causes energy dissipation.
- Difference between emf and terminal pd.
What is resistance heating?
- Occurs due to resistance in components.
- Charge carriers lose energy in collisions.
- Results in heating due to potential difference (p.d.).
What is the hint regarding sources of emf?
- Sources have some internal resistance.
- Neglected if internal resistance is trivial.
- Significant for negligible sources.
What is the total resistance of a circuit with a 12V battery and 1.5Ω internal resistance connected to 4.5Ω resistor?
- Total resistance = internal + external resistance
- 1.5Ω (internal) + 4.5Ω = 6Ω
How is the electromotive force (emf) defined?
- Energy per unit charge.
- Produced by a source.
Formula:
ε = E / Q
How is power \( P \) supplied to a component calculated?
- Formula:
- Energy per second transferred as thermal energy is \( P = I^2R \).
What is required for calculating a light bulb's current and power?
- Use a 6 V battery with negligible resistance.
- Connected to a light bulb parallel with a 6 V 24 W bulb.
- Follows Figure 6 for circuit setup.
In circuits with identical cells in parallel, what determines the current in each cell?
- Each cell provides a current of I / n
- I is the total current
- n represents the number of cells
How is the cell current calculated in a circuit?
- Cell current = cell emf / total circuit resistance
What happens to the terminal pd when current flows?
- Terminal pd is less than emf.
- Difference due to internal resistance.
What factors affect the rate of heat transfer in components?
- Depends on power supplied \( (I^2R) \).
- Heat transfer rate equals heating of surroundings.
- Energy transfer is not temperature-dependent.
How is total resistance in series calculated?
- The total pd is sum of individual pds.
- Resistors in series have same current.
- \( R = R1 + R2 + R_3 + \ldots \)
How does a potential divider supply a fixed pd?
- Use resistors R1 and R2 in series.
- Total resistance: R1 + R2
- Potential difference across R1: V1 = (V0 × R1) / (R1 + R2)
Potential difference across R2: V2 = (V0 × R2) / (R1 + R2)
How does an ideal diode behave in circuits?
- 0.6 V when forward-biased conducts current.
- Infinite resistance when reverse-biased.
What is lost pd in each cell with internal resistance \( r \)?
- Lost pd is \( \frac{Ir}{n} \).
- \( I \) is the total current.
- \( n \) is the number of cells.
- \( r \) is the internal resistance.
What is the cell current if EMF is 1.5V, with resistors of 0.5Ω internal and 2.5Ω external?
- Total resistance = 0.5Ω + 2.5Ω = 3Ω
- Cell current = 1.5V / 3Ω = 0.5A
How do you calculate the total emf for cells in series if they're in opposite directions?
- Net emf = difference between emfs
- If 20V and 15V in opposite, net emf = 5V
How is the total resistance in a circuit calculated?
- Series: \(r + R\).
- \(r\): internal resistance.
- \(R\): external resistance.
What equation gives the current through a cell?
I = ε / (R + r)
where
ε = emf
r = internal resistance
What is the total resistance of a 4Ω and 12Ω resistor in series?
- Total resistance:
How do resistors in parallel share the current?
- Parallel resistors have the same pd.
- Current through \( R1: I1 = \frac{V}{R1} \), \( R2: I2 = \frac{V}{R2} \).
- Total current \( I = I1 + I2 \).
What is the learning objective for resistances in series and parallel?
- Calculate resistances in series and parallel.
- Define resistance conceptually.
- Calculate current, pd for each circuit component.
What is a variable potential divider used for?
- Control loudness: variable output to a loudspeaker.
- Brightness: adjust current to light bulbs.
- Maximum resistance for zero current output.
What is Kirchhoff's first law?
- Sum of currents at a junction is zero.
- Total entering = total leaving.
How is the current calculated across cells in parallel?
- Total current = pd across cells / total resistance
- Sum of individual current values
How is power supplied by the cell expressed?
- \(P = I \varepsilon = I^2R + I^2r\).
- Supplied to \(R\), dissipated in \(r\).
How is electrical power supplied to a resistor calculated in a circuit?
- Formula:
- P = I × V
- with current I = V / R
What does a sensor circuit do?
- Produces output pd from physical changes (temperature, light).
- Uses thermistors or light-dependent resistors (LDRs).
What is the effect of temperature on a potential divider?
- Thermistor resistance changes with temperature.
- Adjusts pd across the variable resistor.
How is the sum of the pds around a circuit loop described?
- Equals the sum of emf in that loop.
- Based on Kirchhoff's second law.
What happens to the total resistance if cells are in opposite directions?
- Total resistance is sum of individual internal resistances
When is maximum power delivered to the load?
- When load resistance \(R = r\).
- Internal equals load resistance.
How is internal resistance measured?
- Use high-resistance voltmeter.
- Measure terminal pd across cell.
- Connect cell in series.
Describe the setup of a light sensor circuit.
- Uses LDR and variable resistor in series.
- Pd across LDR changes with light intensity.
- Higher light decreases LDR resistance and pd.
What happens if cell polarity is reversed in a circuit?
- Total emf becomes 1.5 V less.
- The effect on current is described in examples.
What is depicted in a V vs I graph for a cell?
- Straight line with negative gradient.
- Gradient = \(-r\).
- y-intercept = emf.
The question on the page originate from the summary of the following study material:
- A unique study and practice tool
- Never study anything twice again
- Get the grades you hope for
- 100% sure, 100% understanding
