A change in the gravitational force acting on an object will affect the object
1 answer:
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Answer: R = 394.36ohm
Explanation: In a LR circuit, voltage for a resistor in function of time is given by:
ε is emf
L is indutance of inductor
R is resistance of resistor
After 4s, emf = 0.8*19, so:
R = 394.36
In this LR circuit, the resistance of the resistor is 394.36ohms.
Answer:
Transformers are used to increase or decrease the voltage of AC currents
Explanation:
A transformer is a device consisting of two coils (called primary and secondary coil) wrapped at the two sides of a soft iron core. When an AC current is present in the primary coil, it induces a magnetic field inside the core, and the presence of this changing magnetic field induces a voltage (and a current) into the secondary coil.
The voltages in the primary and the secondary coil are related by the transformer equation:
where
Vp, Vs are the voltages in the primary and secondary coil
Np, Ns are the number of turns in the primary and secondary coil
There are two types of transformers:
- Step-up transformers: these have , so that
, which means that they increase the voltage. They are used to increase the voltage of the AC current produced by the power plants, before being sent into the transmission lines.
- Step-down transformers: these have , so that
, which means that they decrease the voltage. They are used at the end of the transmission lines, before the houses, in order to decrease the voltage and allow the household appliances to work properly (in fact, household appliances need lower voltages to work)