IB · IB Physics
IB Physics: Current and circuits — Practice Questions & Answers
326 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Easy
A resistor of $4.0\,\Omega$ has a potential difference of $12\,\text{V}$ across it. What current flows?
- $3.0\,\text{A}$
- $48\,\text{A}$
- $0.33\,\text{A}$
- $8.0\,\text{A}$
Tap an answer to check it.
WhyOhm's law: $I=\frac{V}{R}=\frac{12}{4.0}=3.0\,\text{A}$.
2
Multiple choice · Medium
A device operates at $230\,\text{V}$ and draws $2.0\,\text{A}$. What is its power?
- $460\,\text{W}$
- $115\,\text{W}$
- $232\,\text{W}$
- $0.0087\,\text{W}$
Tap an answer to check it.
WhyPower $P=VI=230\times 2.0=460\,\text{W}$.
3
Multiple choice · Easy
Two resistors of $3.0\,\Omega$ and $5.0\,\Omega$ are connected in series. What is their combined resistance?
- $8.0\,\Omega$
- $1.9\,\Omega$
- $15\,\Omega$
- $2.0\,\Omega$
Tap an answer to check it.
WhyIn series resistances add: $R=3.0+5.0=8.0\,\Omega$.
4
Multiple choice · Medium
Two $6.0\,\Omega$ resistors are connected in parallel. What is the total resistance?
- $3.0\,\Omega$
- $12\,\Omega$
- $6.0\,\Omega$
- $0.33\,\Omega$
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WhyFor two equal parallel resistors, $R=\frac{R}{2}=\frac{6.0}{2}=3.0\,\Omega$.
5
Multiple choice · Medium
A current of $2.0\,\text{A}$ flows for $30\,\text{s}$. How much charge passes?
- $60\,\text{C}$
- $15\,\text{C}$
- $0.067\,\text{C}$
- $32\,\text{C}$
Tap an answer to check it.
WhyCharge $Q=It=2.0\times 30=60\,\text{C}$.
6
Multiple choice · Hard
A cell of emf $1.5\,\text{V}$ and internal resistance $0.50\,\Omega$ drives a current of $2.0\,\text{A}$. What is the terminal potential difference?
- $0.50\,\text{V}$
- $1.5\,\text{V}$
- $2.5\,\text{V}$
- $1.0\,\text{V}$
Tap an answer to check it.
WhyTerminal pd $=\varepsilon-Ir=1.5-(2.0\times 0.50)=1.5-1.0=0.50\,\text{V}$.
7
Fill in the blank · Easy
The rate of flow of electric charge is called electric .
Answer:
current
WhyCurrent $I=\frac{\Delta Q}{\Delta t}$, measured in amperes.
8
Fill in the blank · Medium
Resistors of $3.0\,\Omega$ and $5.0\,\Omega$ in series have a total resistance of $\Omega$.
Answer:
8 / 8.0
WhyIn series the resistances simply add: $3.0+5.0=8.0\,\Omega$.
9
Multiple choice · Medium
An ohmic conductor at constant temperature carries a current of 0.25 A when a potential difference of 5.0 V is applied. What is its resistance?
- 20 ohms
- 1.25 ohms
- 0.05 ohms
- 5.25 ohms
Tap an answer to check it.
WhyFor an ohmic conductor R = V / I = 5.0 / 0.25 = 20 ohms.
10
Multiple choice · Medium
For an ohmic resistor at constant temperature, which statement is correct?
- Current is directly proportional to potential difference
- Current is inversely proportional to potential difference
- Resistance increases as current increases
- Potential difference is proportional to current squared
Tap an answer to check it.
WhyFor an ohmic conductor the current is directly proportional to the potential difference, so resistance stays constant.
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