Unit 2.3: DC Circuits Flashcards
To measure current, how is the ammeter connected: in series or in parallel?
In series to avoid affecting the current and have negligible resistance
Is the current the same or different across all points in parallel circuits?
Different-the value of the branches add up to the total current.
Explain in terms of current, the conservation of charge
The sum of the currents entering a junction is equal to the currents
leaving the junction. This is due to the conservation of charge.
How are the voltmeters connected to all circuits. In series or in parallel?
In parallel, across the component
How is the conservation of energy involved when speaking about potential difference in a series circuit?
The sum of the p.d’s across components in a series circuit is equal to
the p.d. across the supply. This is a consequence of the conservation
of energy.
What is the potential difference in a parallel circuit?
the p.d. across all components in parallel is the same.
State the equation for total resistance in a series circuit.
Rt=R1+R2+R3+…
State the equation for total resistance for a parallel circuit
1/Rt=1/R1 + 1/R2+..
In a Parallel circuit. The total current input
is equal to the current
through each branch of
the circuit. This obeys what law?
Conservation of charge
In a parallel circuit. The potential difference
across each component
is equal. This obeys what law?
The law of conservation of energy
For a series circuit. The current is equal at every point in the circuit. This obeys the law of what?
Conservation of charge
For a series circuit. The total potential difference input is equal to the sum of the potential differences across the
components. This obeys the law of what?
Conservation of energy
When is a potential divider circuit used?
When a certain output potential
difference is required.
State the potential divider equation
Vout=Vs x R2/R1 + R2
What is an LDR?
A component that has a resistance that changes when light falls on it. As the
intensity of the light is increased so the
resistance of the LDR falls.
What components are often used in potential divider circuit and what does this mean for the total resistance?
Thermistors and LDRs. The total resistance can change because the resistance of these components can change also
What is a thermistor?
A temperature-sensitive resistor. The resistance decreases as temperature increases (usually)
What is the definition for EMF?
The emf of a source is the energy converted from
some other form (e.g. chemical) to electrical potential energy per
coulomb of charge flowing through the source.
State the equationS for EMF
V=E-Ir
V=energy transferred to the components per C of charge
E=Energy transferred to electrical energy in the cell per C of charge
r=Energy lost due to the internal resistance
Units:Volts
What is the difference between EMF and p.d?
Emf is the total energy supplied to the circuit per unit charge, while p.d. is the electrical energy per unit charge converted to other energies by the components.
If n cells are connected correctly, each with emf E and internal resistance r, the total emf will be what? and the total
internal resistance will be what?
Total EMF=nE
Rt=nr
