State Coulomb’s law of force between electric charges - Leaving Cert Physics - Question d - 2017
Question d
State Coulomb’s law of force between electric charges.
A capacitor can be used to store electric charge.
A discharged capacitor with a capacitance of 6 × 10⁻⁶ F is... show full transcript
Worked Solution & Example Answer:State Coulomb’s law of force between electric charges - Leaving Cert Physics - Question d - 2017
Step 1
State Coulomb’s law of force between electric charges.
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Answer
Coulomb’s law states that the force (
F) between two electric charges (q₁ and q₂) is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance (r) between them. This can be expressed mathematically as:
F ext{ } ext{ is proportional to } rac{q₁ imes q₂}{r^2}
Step 2
What is observed when the switch is closed?
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Answer
When the switch is closed, current flows in the circuit. This results in the capacitor charging up, causing the bulb to initially light up. As the capacitor charges, the current reduces, and the bulb may eventually dim.
Step 3
What would be observed if a 12 V a.c. power supply had been used instead?
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Answer
If a 12 V a.c. power supply were used, the bulb would continuously light up and dim as the alternating current (a.c.) oscillates. The capacitor would charge and discharge with each cycle of the a.c. supply, resulting in a fluctuating brightness.
Step 4
Calculate the charge stored on the capacitor when it is connected to the 12 V d.c. power supply.
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Answer
The charge (Q) stored in a capacitor is given by the formula:
Q=CimesV
where:
C is the capacitance (6 × 10⁻⁶ F)
V is the voltage (12 V)
Substituting the values gives:
Q=(6imes10−6extF)imes(12extV)=7.2imes10−5extC
Thus, the charge stored on the capacitor is 7.2 × 10⁻⁵ C.
Step 5
State one application of a capacitor.
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Answer
One application of a capacitor is in filtering circuits, where it is used to smooth out fluctuations in voltage, as in power supply circuits.
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