Electricity Flashcards
How do objects become negatively charged?
A substance that gains electrons becomes negatively charged
How do objects become positively charged?
A substance that loses electrons becomes positively charged
What happens when similarly charged objects come close to one another?
Two charged objects will repel each other if they have the same type of charge (they are both positive or both negative).
What happens when differently charged objects come close to one another?
Two charged objects will attract each other if they have opposite charges.
What is current? How is it measured?
Current is a measure of how much electric charge flows through a circuit. The more charge that flows, the bigger the current.
Current is measured in units called amps using an ammeter.
What is potential difference? How is it measured?
Potential difference is measured in volts, V.
A potential difference, also called voltage, across an electrical component is needed to make a current flow through it.
What are the common circuit symbols?
See book.
How is resistance calculated?
Resistance is measured in ohms.
The total resistance of a series circuit is the sum of the resistances of the components in the circuit.
What is the relationship between current and p.d for a resistor at a constant temperature?
The current flowing through a resistor at a constant temperature is directly proportional to the potential difference across it. A component that gives a graph like the one to the right is said to follow Ohm’s Law.
How does current behave in a series circuit?
When two or more components are connected in series, the same current flows in each component.
How does current behave in a parallel circuit?
Components that are connected on separate loops are connected in parallel.
The current is shared between each component connected in parallel.
The total amount of current flowing into the junction, or split, is equal to the total current flowing out.
The current is described as being conserved.
How does potential difference behave in a series circuit?
If there is a change in the resistance of one component then this will result in a change in the potential differences across all of the other components in the circuit.
How does potential difference behave in a parallel circuit?
When two or more components are connected in parallel, the potential difference across them is the same. This means that if a voltage across a lamp is 12 V, the voltage across another lamp connected in parallel is also 12 V.
How is the total resistance of resistors connected in series calculated?
When resistors are connected in series, the current through each resistor is the same. In other words, the current is the same at all points in a series circuit.
When resistors are connected in series, the total potential difference across all the resistors is equal to the sum of the potential differences across each resistor.
The total resistance of a number of resistors in series is equal to the sum of all the individual resistances.
How does the resistance of a light-dependent resistor vary as it is exposed to light?
In the dark and at low light levels, the resistance of an LDR is high, and little current can flow through it.
In bright light, the resistance of an LDR is low, and more current can flow through it.
